You're touching on a nuanced but important point in electrical installations and NEC compliance. Let's break down the issues

NEC Requirements for Receptacle Grounding and Metal Boxes
General Rule

When a receptacle is installed in a metal box, the box must be effectively grounded. This is because a fault in the receptacle could energize the metal box, creating a shock hazard.

Grounding Methods

NEC provides several acceptable methods for grounding a receptacle in a metal box. The most common is to use a grounding conductor (equipment grounding conductor or EGC) that runs with the circuit conductors and connects to the grounding terminal of the receptacle and to the metal box (typically with a grounding screw).

Self-Grounding Receptacles (the crux of the issue)

The NEC does allow an exception (NEC 250.146(B) in the 2023 edition) where a receptacle can ground to the metal box through its mounting screws

IF certain conditions are met. This is where the "listed for bonding" language comes in.

Key Points About "Listed for Bonding" (Self-Grounding) Listing Requirement

The NEC requires that the receptacle and the box be specifically listed for grounding to each other through the mounting screws. This means they have been tested and certified by a recognized testing laboratory (like UL) to ensure that the connection is reliable and safe for grounding purposes.

How to Know if Listed

Look for markings on both the receptacle and the box that indicate they are listed for this type of grounding. These markings are usually on the product labels or stamped into the metal. If these markings are not present, you cannot rely on the mounting screws alone for grounding.

Rarely Found

In practice, it's very rare to find both a box and receptacle combination that are specifically listed for this method. The default assumption should be that you cannot rely on mounting screws for grounding unless you have positive documentation (listings) saying otherwise. Always install a grounding pigtail.

The Role of Raised Faceplates They potentially provide additional contact surface

A raised faceplate, especially if it has a large, flat surface that contacts the receptacle's grounding strap, might provide a greater surface area for electrical contact between the receptacle and the box. However, this does not automatically qualify it for self-grounding.

It's about Listing, Not Just Surface Area

The issue isn't just the potential for better contact; it's about tested and certified performance. A lab needs to verify that the combination of receptacle, box, and any faceplate (raised or not) is a reliable grounding path under fault conditions. Without that listing, you can't rely on the mounting screws alone.

Flat vs. Raised Doesn't Guarantee Anything

A standard flat receptacle faceplate is also not automatically approved for self-grounding. It's all about the listing.

Why the confusion/risk? A faceplate manufacturer might create a raised faceplate intending for it to aid grounding, but without actual listing, it does NOT meet the NEC. People (including the graphic you saw) might incorrectly assume that a "beefier" faceplate is sufficient, leading to unsafe installations.

In Summary Always Ground

The safest and most reliable practice is to always install a grounding pigtail from the metal box to the grounding terminal of the receptacle.

Don't Assume

Do not assume that any receptacle, box, or faceplate combination is approved for self-grounding unless you can verify it with listing information.

Grounding Pigtail is the Best Practice

The cost of a grounding pigtail and the little bit of extra time it takes to install are minimal compared to the potential consequences of a grounding failure.

Raised Faceplate Considerations

The presence of a raised faceplate does not change the need for proper grounding. Its presence is immaterial unless the entire system is listed for self-grounding.

How to Check for Listing Manufacturer's Documentation

Check the product's packaging, labeling, or the manufacturer's website for information about grounding listing.

UL or Other Listing Agency

Look for the UL (Underwriters Laboratories) or other recognized testing laboratory symbol and a listing number on the product. Then, verify the listing details on the UL website or the listing agency's database.

Bottom Line:

The graphic you saw is potentially misleading. Unless you can definitively prove that a receptacle and metal box combination (with the faceplate included) is listed for bonding, you must install a grounding pigtail from the box to the receptacle's grounding terminal. Relying on mounting screws alone without proper listing is a code violation and a safety hazard. When in doubt, always ground. Flag for review