Yes it is, but the evidence is non-specific. China will attempt to cover up 100% of lab leaks. China may attempt to cover up zoonosis. The cover up is consistent with either theory, but it is the only reaction consistent with a lab leak.
China attempted information control on SARS-1, but rolled most of it back by April. They still haven't done this for SARS-2. That's not proof, but is a difference. Enough small differences can add up to a large difference.
this is a blind assumption. they may just be covering up 100% of all things, especially when the international community (i.e. Trump) is trying to push/blame them.