Why it's not reasonably possible for you to be banned by Bloxstrap
This page directly addresses what happens in the event of banwaves, where Roblox collects detection vectors from users overtime, and then by surprise, wait and take action against every user who's been detected, all at once. This happens every month or so, rinse and repeat.
Roblox does this in order to specifically combat exploiters and cheaters on the platform. They only have reason to target just that specific group of people, for obvious reasons.
There's a really unfortunate ambiguation here: People that have been hit by a banwave will receive this moderation note, or something like it:
When they say "third-party software to modify the client", they mean tampering with the Roblox Player process/executable. In other words, in the manner that exploits and cheats do. That's just how they formally describe it. It is a painfully vague message, but it is not referring to Bloxstrap or applications like it.
Exploits "modify" the client by attaching to the Roblox Player process and invasively screwing around in its memory space, etc. This activity is what Roblox is looking for when they ban you, and Bloxstrap does not do it at all.
Bloxstrap can "modify" the client by just making it easier to replace local content files, for stuff like custom textures and sounds, etc. For clarity, the Fast Flag system is an official part of the client, and all flags are officially defined by Roblox. We just make it easier to use for us enthusiast players, and you cannot be banned for using it like this. Read more about that here.
Sure, you can both call them "modifying the client", but they are two completely different things. Bloxstrap does not at all do anything to the client that can get you banned. Roblox is not out to hunt down people who wanted to change their death sound or whatever.
Furthermore, Roblox staff themselves understand this and have clarified this, similarly stating there is no reason for Bloxstrap to get you banned.
https://devforum.roblox.com/t/welcoming-byfron-to-roblox/2018233/693?u=xtremeguy2256
If you were banned from Roblox under the presumption of using exploits, it is certain to say that it was not because of Bloxstrap.
Don't be this guy.