Lee Carré (2021-07-02 02:11:25+00:00): “Maybe for economy, you could just use one "source=survey", since all the facts come from your survey. Only if some tag has another source, that could be indicated with a separate source:x=y”
I have certainly considered that.

I'm thinking about when someone else edits it, though. Being unspecific would cause ambiguity.

Notice that for frequency, while I do add what is very likely to be the actual value, I never include source:frequency=survey (since it's just a guess).

I'm also hoping that by doing it this way, overly-keen newbies (throwing caution to the wind) will (might?) leave alone the ones marked as coming from a survey, even if they mess around with others (which aren't so marked).

I don't mind being verbose, for the sake of accuracy & precision. Hopefully it keeps things clear for other mappers, too.

I'm reminded of when, for the multi-storey carparks, I went to the Parking Control Office to ask what the capacities were (counting the spaces of a small surface carpark is one thing, but a multi-storey (with several hundred) is another).
Surprise, surprise, they didn't match the values in OSM. It wasn't even a predictable offset (e.g. excluding spaces for the disabled, in cases where I'd counted those (few) during survey).
Since there was no citation of where the OSM numbers had come from, and being less than keen to go through the history to find the changeset which added (or list changed) the capacity in order to check what the changeset's source tag stated, I replaced the valve in OSM and promptly added source:capacity(=Parking Control Office).
Thus, instead of being some arbitrary number, if someone wants to dispute the current value, they'll have to see & raise my source with an actual survey. But, short of doing the tedious walking along every floor in a grey concrete box, I'll take the number given by the folks who administer the place, over a number of dubious credibility.

“I think official_name is not needed since it's the same as the main "name".”
Similar to above, this came from witnessing disputes over exactly how roads should be named (seemingly regardless of what signage says). Some folks want OSM to match old (paper) maps. Thus, I started using official_name, short_name, and others; seemed best to avoid conflicting preferences, since the solution becomes making one's favourite tool use whichever tag one prefers instead of having an endless edit-war over the value of the name key.

If someone wants to mess about with name=* then so be it, but at least official_name might still be preserved.

Since there are cases for which the official_name and the colloquial name differ (Springfield Stadium comes to mind), setting both makes it clear & confirms that what's rendered is actually the proper name.

If official_name weren't set, then what is name exactly? My interpretation of what to call it?

Though, thinking about it, official_name should actually be exactly what appears on the sign (which is all-caps, for starters), while I would keep it Title Case for regular name (for readability).
So, they should be different by nature.

To me, this is another instance of accuracy, throughness, and completeness over convenience.

Compare, perhaps, someone setting opening_hours:covid19 to match opening_hours. One could argue redundancy, but it makes explicit that they're unchanged. Without *:covid19 it remains uncertain if they're the same, versus if someone simply hasn't yet added the differing hours.