I remember the old records used to refer to singers as "vocal accompanist", and it's true enough that there are musical genres where that is an appropriate way of thinking about their role. Bluegrass is probably one such genre. But more typically it's the people playing the musical instruments who are the accompanists, at least while the singer is actually singing. And the skill of an accompanist is to follow the person or instrument they are accompanying.

That doesn't in any way mean there aren't skills a singer should aspire to learn - but those skills don't necessarily make it easier for an accompanist. They can even make it harder - for example when they include variations in timing, as an essential part of the storytelling.

This all reminds me of the discussions about percussion, where it becomes clear that, in some types of music, the drummer lays down the beat, over which the other musicians do their thing (including the singer), while in other types (including Irish music in particular) it's the other way round, with the drummer following the lead of the singer or the fiddle or whatever.