Surely some borrowers and lenders make decisions about making and taking loans based on the actual interest rates on the actual loans? In which case it doesn't

Surely some borrowers and lenders make decisions about making and taking loans based on the actual interest rates on the actual loans? In which case it doesn't matter so much if the rates are calculated based on a fictional assumption about something. At the end of the day every borrower or lender in the market makes their own decision about which lending contracts they take part in.