It looks like total bullshit making stuff up on the fly.
He read the original customers tweet and rather than ignore it he decided to reply. Then misjudged how his audience would take his his tone and and got push back with people agreeing that they preferred single sex.
If he is a good business man who used a talent to financed a new build, his capacity for seating customer's is a key element for a sucessful business.
What is his maths on his cash return on 1 seat so,
1 brunch,
1 lunch,
1 early and
1 late dinner by
× open days by
× average occupancy by
× profit of a service?
You can bet he has a number and all kinds of controls to make sure that he is hitting targets.
If the decision was not taken lightly he should know his obligations as an employer.
For hygiene reasons I would expect that staff have single sex changing facilities including lockers and single sex toilets away from customers.
So for the funder/ employer he has to provide for space for each sex, and do the maths that is at any given time the split will not be 50/50. An additional toilet or changing space is a reduction in 1+ seats.
If the decision was not taken lightly he should know his obligations as a provider of services and have worked through the in's and
outs's of the reasons for the additional space needed for disabled customers or more importantly how much room walkways and one extra unit takes from his sales floor. There is no point in having them if the customer can't get to and from their table.
He could try not to bullshit on twitter about some non-existent religion which requires a single sex, single occupancy unit because women(men?) are not allowed to stand together at the sinks.
If anything that comment suggests that a senior staffer decided that they should be given access to the faculities for the other sex and the space savings made for a more profitable business.