Has this come up before?

No, this is the first time I'm asking people about this.

Why ask? If it hasn't come up, people don't think you're BS; if they thought so, trust me, you'd hear about it. If you're the one to bring it up, people will think you're speaking from a guilty conscience (why bring it up if you didn't have something to hide, etc).
Not saying I think you're BS, because I don't. Just wondering why you'd ask, or even care, what other people think.

I usually don't do something like this, but I saw in forum that some people do doubt about me.

Oh, well, you're fairly new and have good FGO scores. It's a typical reaction from them. Considering your history with 7-key timing games though, it shouldn't really be a big mystery how you got good in little time.
Also, some of them have been called BS themselves, so they're bitter and want to cause the same pain to others. Making the cycle go round and round...

Even if you were bs who gives a shit?
It's just a low-end online flash game.
Your stats are definitely looking beautiful though ^^ nice job!
You're pretty damn good o.o
Do you track your tiers?

I don't really track my tier points, but one day I saw it and the score was pretty good. (304)

yes o00o no

you are bs