Read Receipts still showing???

Hello. I sent a message to someone on an my iphone 12, and it says delivered. However, previous messages still give a read date. Is it possible they turned off their read receipts, or have they just not read it? I don't know if read receipts are retroactive and will revert, IF you switch the setting back to "off".

I am also confused, as to how they could just turn off the setting (I know it is an individual thing for me) without actually seeing the message? Thank you!