Yes, 744 reallocations would concern me.
“Reallocs” are sectors on the hard drive that have gone bad and been replaced with spare sectors. A few on an old mechanical drive may not mean immediate failure, but 744 is a lot and I wouldn’t consider that a healthy drive.
More importantly, if the seller’s photo showed 0 reallocs for this iPod and it arrived showing 744, I’d contact the seller and ask for a return/refund rather than rely on that hard drive.
If you can, also post the complete diagnostics screen, especially the Reallocs, Pending Sectors, and PowerOn Hours values. That would give a better picture of the drive’s condition.