Double zoonosis? The virus jumped to us and then to dogs, cats, tigers, hippos, pigs, etc. 29 known species! An unfathomable triple zoonosis that happened many, many times (thousands?) over the years. I’d say double zoonosis isn’t too uncommon.
The initial SARS presumably passed from bat to intermediate host to humans in a wet market. This exact type of event happened in China just 20 years ago.
And there isn’t “no trace” of an intermediate host. There are suspected intermediate hosts but none confirmed. Similarly SARS had a couple potential intermediate hosts, and MERS had a potential intermediate host but unanswered questions around that, too. Scientists had more confidence in those theories, but still uncertainties.
Again, I think both theories are plausible. But being a repeat to what we’ve seen before _is_ simpler. When you hear hooves, think horses not zebras.
Put another way, the simplest explanation that fits the available evidence is most likely to be correct.
At this point it seems to me that a lab origin looks rather simpler than a market origin with double zoonosis and no trace of an intermediate.