> Comprehensive studies on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by Member States suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms.
> The available data, to date, on onward infection from cases without symptoms comes from a limited number of studies with small samples that are subject to possible recall bias and for which fomite transmission cannot be ruled out.
Go looking for evidence on the internet I suspect anything can be supported. I stopped trying to keep up with the evidence a few months ago; but certainly as of May I was infuriated by how little actual knowledge seemed to be disseminating about how, in detail, this thing spreads.
There is a lot of 'common sense' out there that appears to be unsupported by attempts to gather and work to evidence. I havn't seen anything so far to suggest that asymptotic transmission is the problem. My theory is that people are ignoring quarantines if they have mild symptoms - but again, no evidence.