I can confirm this behaviour on Sailfish OS 4.5.0.24
Just for curiosity, I flashed (*) the “old” previous image Sailfish OS 4.5.0.18 and in this case Bluetooth is working fine, I was able to be detected and pair with my other phone 
So this is clearly a regression of this version…
(*) Here is what I did: from SFOS 4.5.0.24 go to TWRP, format data, mount system, flash zip and reboot
NOT flashing hybris-boot again, NOT flashing factory FPOS Android 11 either.
(I made a TWRP backup of /Data partition before format data)