It's even happened pre-AI https://en.wikipedia.org/wiki/Tokyo_subway_sarin_attack
Again the same logic applies though, it takes significant effort and money to create sarin, it requires a lot of rigor. That is the limiting factor, not the knowledge of how to make it.
If we are worried about people making sarin in their garage we can do many things to control the supply of chemicals needed to make it. We don't need to try to restrict knowledge of chemistry.
"regulation of current models" basically implies that open source models will be heavily restricted if not banned outright and guarantees that intelligence will be owned and gatekept by a duopoly.
So if I have to choose between the slim possibility that a crazy person might develop a bio-weapon and the possibility that Anthropic, et. Al convince the government to regulate and control open source models (because I'm sure the government will only do that for good reasons and never things like covering up scandals, squashing dissent or enhancing their own power) and any competitors. I'm probably going to put my chips on a nutcase in a trailer park developing super sars over regulator capture by the government.
Let's look at it in an inverse way. Making a single drug that impacts a single protein, intelligently, from the ground up, has arguably never actually been done. Despite unbelievable financial incentive. And with AI.