‘such reid would make them an eino modeh b’eruv”
I don’t think that is exactly the definition of אינו מודה בעירוב which was originally for צדוקים who don’t believe at all about the very concept of Eruvin. It might be silly reason, given the above, but they do make Eruvei Chatzeros in their driveways etc – so how can they be labeled as “eino modeh b’eruv’?