Well I have used the APP powder - many years ago. It clot and clumps very easily and it is under powder.
This a picture of a new bottle open for use. Notice the large clump in the picture and there were more in the bottle.
Another new bottle showing a large clump at the top of the powder
The next bottle I opened came with a moisture absorbent pack in the powder - I think that is a good indication APP knew it was a moisture sucking powder.
At $10 - $12 a bottle is kind of was OK for these clumps to appear and you didn't feel real bad crushing the clumps. Still the powder did not meter out to a volume measure very well. But at $25 a bottle - there are such better powders available.