Think based on bathroom rather than bed count here.

Before: sell two business travelers one room with two separate beds and one dignified bathroom.

Now: sell two business travelers two separate rooms just so they can each use the bathroom with dignity.

Profit Now ($x2) > Profit Before ($x1)

This still makes no sense.

The business travelers are looking at a website with hundreds of hotels in the city they're going to. If you don't offer a twin room option, they don't think "well shucks, let's just get two single rooms". They go to the next hotel, out of hundreds, which has a twin room option. It may cost more, but it won't cost double. They'd be complete idiots to pick two single rooms if what they wanted as a twin room.

You can't compel them to book your single rooms, and you definitely can't compel them by springing a surprise doorless bathroom on them in your twin room option after they've paid and arrived. That's when they expense a taxi to some other hotel and report their findings to their entire company, who never book from you again.

Simply offering a twin room option means you expect unrelated or distantly-related people will book it. If you don't want that, take away the twin room option. Business travellers will not share a double bed. You get all that benefit of double-profit (if for some reason the travellers are morons or they're going to bumfuck nowhere and you're the only hotel), without going to the expense of removing bathroom doors.