I’m not going to recommend using non-Type CC Instant Start ballasts with non-Circle I lamp sockets as it is not UL-compliant, thus not code-compliant, fixture construction.
I will.
Not to get nit-picky, but your comment is only true in new fixtures, by UL requirement.
For those that are retrofitting, relamping, changing from T12 to T8 or to T-LED, there is no code issue, so it's perfectly OK. I point this out because the question was posed and because alot of forum members do these types of changes. There is no reason for them to needlessly seek out different sockets (a hassle and an expense) and to do alot of extra re-wiring to accomodate the new tubes.
CD
Without question - the Best Bang for the Buck ever 