MacBook Pro stuck on Apple logo, Disk Utility first aid and fsck ok
Your thinking is correct.  It’s likely the hard drive, however it could also be SATA cable. Given that it’s inexpensive, it makes sense to charge it out with the replacement drive.

However, to know for certain, connect your drive to a USB to SATA adapter, if the drive works properly, then you have proof positive it’s the cable.

Doing diagnostics on a drive with an “unknown” working Component could give you erroneous results.