No it's not a bug, the Revi gunsight shows the reticle always at the same size, no matter how far or what angle you look at it.
And no, it doesn't affect your shooting. It would affect if it would change size
The reticle rings have to stay the same size regardless how far you look at it, otherwise you couldn't assess the target range correctly.
Good vid .. and no, this isn't a Revi in the vid but the principle is the same: