I like using threads, some BB shells have a plain hole cause the original plastic guide came with a "split plug" similar to a lot of automotive fittings for trim and shields (that typically fail, but that's another rant). If it's "missing" threads I add them, not trusting "self-tapping" screws or sheet-metal or wood threads.
YMMV
I find I almost always need to trim the length of the (always SS) bolt or machine screw, but I'm used to doing that.
I've found many Shimano guides came in purple (as well as black or blue) and always a bit mystified as to what the "other hole" was for: I always use the one that fits road bike shells (68 or 70mm) and cannot figure out why the second, unless for a VERY wide Mtn bike shell?