The equipment and ppe for bio weapons and chemical weapons of the same health hazard is about the same. The only difference with biological weapons is you're doing stuff with fridges, incubators, agar, and petri dishes, rather than beakers, Bunsen burners, and filters.

In either case your logic is relying on a threatening actor to not have any education. Sure, the pool of candidates is lower for sophisticated say, anthrax, something you can almost trivially find in dirt, but it's also lower for sophisticated chemical weapons like say, sarin. And keep in mind, yes it's hard to do biology or chemistry, but devoted individuals do it in garages, for often innocuous reasons. You can't just assume some terrorist group will never have a strongly devoted individual or group who are competent enough to pull something off, you need to have preparedness. (In the form of local procedures, drills, and organization and plans and equipment to respond to threats as they develop, along with preventative measures)

Also make no mistake, spotting lab scale chem and biological warfare production is extremely difficult. Even moreso for biological production, but both resemble conventional labs (and could be!). Where biological becomes an issue is that lab scale production of a pathogen can self propagate in a way chem attacks or bomb attacks can't.

I'm not saying to be afraid, the barrier to entry on all weapons production is the lowest it's ever been, but sophistication in preventing them is also quite high. But it's not something that can just be brushed away, it's a real problem that real professionals are continuously solving.