Oh that's so cute and clever. Nice idea ! My budgies have a couple toys with mirrors, and they haven't caused any problems, but if they started to I'd remove them right away.
Yeah it was just because he's alone and just in case he got too obsessed with it. If it was just part of a toy I probably would have left it but since it was literally just a big mirror with a perch I thought I'd be safe and just take it out.