The heads aren’t categorized as A or B heads by weight. There are 2 degree up lie heads to fit specified lie angles from -2 degrees to +4 degrees from standard lie.

Due to manufacturing variations, there are multiple range bins the heads are placed in. I think it is at least 3, Their build then triages heads in a bin for specific orders. The heaviest are used for shorter clubs to get within the range of swing weight. In the build cycle, each head then has a weight added in the hosel to get to the swing weight based on the shaft and grip ordered. Due to variations in head weights from manufacture, each head in a set will likely use a different weight for each club
Clubs built longer than stock will start with lighter heads. The process does not include grinding off weight. Say the B bin is the closest to spec heads. While building stock sets to go to retail but that bin is low, they can use heads from the lighter head bin and add more weight to achieve the specified swing weight. But SW, loft, and lie are all adjusted to tight tolerances and recorded for every club shipped. While your clubs are in production and you lose one, they don’t just grab another 6 T100, they build a new one to the exact specs as your original.