Next we need to talk about "match". Match barrels, match reamers, match rifles, etc. Match seems to mean different, not better as many folks interpret it. It might be better for one thing, but not another.
Custom is tricky...if I put a prefit match barrel on an origin action, put it in a chassis...Then the whole thing shoots 0.2" @100 yd groups with boring accuracy, is it custom?
Then, there is bespoke where someone take a 1/2 finished action, hunk of wood and a pretty good barrel.....then with many hours of woodwork, metalwork, machining, and finishing, a work of art with practical capability is built in Is completed.
I think the challenge is that people associate custom with better than factory....Many times custom is a slower process with similar results. A slower process always costs more.....it doesn't have to be better. That is what I see with tons of custom AR15's. Cool forearm, cool small parts, overly complex BCG, $80 barrel and $100 trigger. Fine custom rifle, I guess, but performance is likely worse than factory.
What do you want "custom" to mean? Handwork? Machining by builder? Accurate? Pretty? Something you cannot do on your own? I think many people apply one or more of these things.
I am having a "custom" rifle built. It will have some handwork, some machining, pretty,.....I cannot do the work well enough. It will probably be very accurate. Is it custom? To me, yes. To some, it will be a Win 70 in a B&C stock with a decent barrel and wildcat chamber. Custom is really a clue that you need to better understand what you are buying/receiving....there is no spec, except what you and the builders work out.