C'pete,
The Hella lantern has the tri-light in the prescribed separations: green - red - and white stern running light - with a seen from dead ahead separation of the red and green. A slight blank space.
It also has, SEPARATE from the tri-color combo, an ALL ROUND WHITE, on top of the combo. It is a separate light but in the same lantern. This light would NEVER be turned on while the tri-color was being used. And viceversa.
Being an all round light, and UNABSTRUCTED by mast or sails,
I have seen, have downloaded, diagrams like yours above here that show this all round white (USCG Regs) USED AS A STEAMING LIGHT ON A SAILBOAT (but with sails not rigged) when the motor is running.
Imco it would be 'more' legal' than a half mast steaming light that would have 1/3, at least. of the all round requirement obstructed by the mast it is mounted on.
And in a twilight ballet of getting the boat into its berth without running into something, no reg could possibly care if the rags are up or furled. Never know, tho.
Your series of graphics don't show this. And since the tri-color option is relatively new (what, 20 years by now?) the Coast Guard may not have their diagrams up to date. Besides the all round white steaming/anchor light may be stuck in some internal committee and is left in its fuzzy status for decades to come.
Perhaps by sailor use the added FOURTH light on the masthead of a sailboat will become written into regulation. It seems to be allowed by inference and some 'quasi-official' diagrams.
The all round white is already wired on some lanterns as a STROBE light. On the highseas, day or night, with an approaching freighter, switching the strobe on to get attention might save your and your boat's butt.
Regs might someday be rewritten to include emergency scenarios like this as emergencies. Using the strobe to get the attention on the bridge of a cargo freighter. Fat Chance! Radio contact with the freighter would call off any rescue effort or USCG notification that assitence was not needed. If that is the case.
The all round anchor light from a practical aspect has to be stacked on the masthead above or below the tricolor if we have one. Cruisers forums often mention that they can recognize their boat at night - when away from it - by their all round led.
This anchor light can also be found with a PV Sunset On/Sunrise Off feature.