That statement hardly supports any position at all since you didn't provide a link. And no.

None of these details are moot if you want to design something. Most of them are moot if you want to throw things together and hope.

The load might be heavy for a doorbell transformer. You're generalizing about something that has to be specific.

You're also not using the plural to name your locations, so you're assuming that one transformer location and probably one transformer is all that will be needed. During my search for parts at the start of this adventure, I only found transformers that output as much as 50VA. That's not enough for six doorbells, so if those are the largest available transformers, it can't be done with one transformer. This means relays MUST be used to separate AC secondary circuits or transformers must put in parallel (which is not a good idea).

An advantage of using relays is that the actual AC secondary wiring can be shorter than it would be if there were only one transformer location.