When AHCI mode is disabled (AFAIK it's a default mode of many currently working BIOSes), SATA drive doesn't have a special system flag (REMOVABLE), so it can be only disabled, not safely removed. If I'm not right in my sentences, please correct me. Currently we do not have plans to fix this problem...

Srdjan, Thank you for your message! In a 2-3 weeks we will release the version that will probably support removal of such SATA drives like yours. If you are interested in beta-testing of the functionality we can notify you when we release the beta-version. P.S. Honestly we are also going to remove ...

I think that you are already aware of this problem in the latest build of Safe removal (4.0 beta 4). After complete unlocking, the program cannot see any other locking handlers on this disk, but still cannot remove it while displaying the nonrelevant message about drive may be under another account ...