How shady are hotel booking websites?

I just booked a hotel from one of the well known platforms. I used my credit card that gives me a 15% discount. But once I booked, there was a custom remark on the booking that requests a smoking room. I don’t smoke and I didn’t write that remark at all. The hotel is entirely non-smoking as well. Everything seems like a dark pattern to me. I felt for this exact trap once a few years ago as well in Japan. Is it just me or is this a common practice for these websites to earn money?