Would it, though? I doubt that these days Rosemary Clooney has much more of a following than Anthony Braxton. It's not like it's a Mosaic of Miley Cyrus or somebody. I imagine the motivation is the usual one: artistic.
I'm inclined to agree. Mosaic are very effective at producing sets which provoke/enable critical re-evaluation of an often underestimated artist and I suspect that this set might be one of those. It also seems to be in line with their well-established 'mission' to produce high-quality vocal-oriented sets - Four Freshmen, Mildred, Dinah, Vaughan, Mercer etc.