Key acceptance means nothing

Key acceptance means nothing. The buyer only signs to say how many keys he/she got from the seller.
The KEY (crucial part) is the walk through agreement. If the buyer signs it, the unit is deemed acceptable. Most of the time, the walk through agreement is attached with conditions for the seller to fix something. Before time of close or move-in, the seller MUST fix those attached conditions or get buyer's extension, otherwise the seller may face charge of breaching of contract/agreement.