The law allows exemptions to the statutory requirement to wear a mask. No part of that requires any business to respect those exemptions, because any business can be stricter than the law if it wishes - even, for instance, when mask law is eventually wholly abolished, it would be totally legal for any business to choose to retain a requirement if they wished. The exception to this is if it involves a legally protected characteristic, which as I said tends to be narrower than many people think it is.
A law could be passed stating "no business may require people to wear a face covering other than under the provisions of this law", but the fact is that it has not been.
(It amazes me just how many people think all discrimination is undesirable and illegal. I wonder how those people think job interviews work?)
Like I said, I disagree. If a business were to refuse serving someone because they couldn't breath properly through a mask I feel that would be beyond what they could & should mandate. If were ever in that situation, I would certainly pursue the matter.