The lab leak hypothesis means "accelerated evolution" through either caged animals or "in vitro cells" infecting the lab personnel. Gene splicing and such are not necessary to make the argument.
The observed fact pointing to this is the number of generations required to produce the divergence between the first SCoV2 variant and the closest wild ancestor. It corresponds to something like 20 years (?) of evolution.
What's notable about the SCov2 variant is how well it spreads between humans. It probably has made the jump many times, it's just this time it figured out how to spread.
"...zoonosis (a disease communicable from animals to man under natural conditions)." —Laurie Garrett, _The Coming Plague_ (Ch 14, section IV)
Which is naturally how the word is used virtually all the time.
Transmission from lab animals kept for study in a biolab, you could argue either way. Transmission from humanized lab animals purposely subjected to serial passage is not really zoonosis in any reasonable sense.