Your points about enterprise support are fair but I was more talking about people that believe that FOSS is inherently less secure than something closed source controlled by a single large company (i.e. security by obscurity which doesn't actually work)

Honestly I do agree in some ways support is better for enterprise products but at the same time companies could still use some sort of source-available license to promote transparency/security auditing while having the same control as a closed source product. It's not FOSS but would definitely be better than having everything closed off