I have plastic excluders and the bees appear to have no trouble going through it. One excluder is used just as it comes. The other I put a thin frame around it.
I did have some dead bees on it last time I checked - but those were bees that got smashed by bur comb on the bottom of the super frames (some were caught half way through - could look like they died in it).
Bees may appear not able to get through but it is probably more likely they need to get used to it. I had an excluder on with a super and fed, they drew almost all the frames in 10 days. (I of course had to clear the comb of syrup so I could use it for honey).
There will be a lot of opinions not to even use excluders - you can of course try them and decide.
If a bar on the metal excluders bends, the queen will slip through... but then plastic can break and fail too.
They used to make punched zinc excluders - but I haven't seen any around.
Mike