Thanks, it is excellent to hear that the Reinitialize disk surface test increased the health back with even 90%, wow!
I mean that yes, generally it designed to improve the usability of the hard disk drive, stabilize the problems and make it better (and ideally improve the hard disk health too) but usually it is rare to see a hard disk with as low health as 8% to increase back to 98%, this seems a bit too good
I mean usually we can't expect too much from a hard disk with 8% health only, usually that may have too much problems to be fixed/stabilized.
Yes, if there are no new problems/issues and (which is more important) no further changes/degradations in the health, then the hard disk could be used - but I'd recommend to do only with constant monitoring and backup upon any possible change, any possible new problem reported.
Personally to be safe, I'd surely perform (now, after the status seems much better) these tests too:
1) Disk -> Short self test
2) Disk -> Extended self test
3) Disk -> Surface test -> Read test
which are recommended in addition to the already used Reinitialise Disk Surface test at
Support -> Frequently Asked Questions -> Hard disk health is low or recently changed or I just installed a new (used) hard disk. How can I perform a deep analysis?
( https://www.hdsentinel.com/faq.php#tests )
If you use Report menu -> Send test report to developer option (even now and/or any further tests or normal use) I can check and advise - and if the tests show no problems, then I can assist to restore the health even back to 100%, to be notified about possible new issues only, as described on