anime Company made amv's

[Nya-chan Production]

then if you think about it the op and the ed of the anime you watch are somewhat like amvs rite

They're a bit different - at least 99% of them are using animation specifically drawn for the OP/ED sequences. It's rare to find even small segments that are reused in the actual series.

Well, sincerely, it's not that rare. Sadly though, reusing these is mostly a result of small budget, so the quality usually isn't high.