The restock times are accurate for the most popular shops, because I can guarantee that some of them have someone ABing at all times. In others, perhaps half of restocks are clocked and recorded. In yet others, perhaps none. I'd be surprised if the database had last restock data for the tikitack shop, unless we still use that to determine RS bans

Also, if our ABer brethren have their refresh rates set to a sane level, they might not catch every item in the restock, particularly the r99s and the like that are bought first.
If you've ever RSed manually, you'll know that the items that restock sometimes (perhaps often) don't all show up at the same time, they might be two or three seconds apart. That can also affect if and when our ABer brethren detect and record a restock.