This topic comes up with the same regularity as the topic of getting live primers out of a case.
The primer topic always splits about 50-50, between those of us who just push out the live primer and those who think the practice is dangerous and won't do it.
The sizing a new case also splits about 50-50, between those of us who never size a new case, unless it is noticeably damaged, and those people who always resize and trim a new case.
My take is that when we buy Remington brasss, for example, it comes out of the same machine that supplies their loading equipment that makes the ammunition they load into little boxes and sell to the shooters.
Does anyone think our little press on the bench that we screw dies into, can do a more precise job of sizing the brass, than can the huge, prescission made machinery the factory uses?
I don't think so.