A customer came in to my shop, stained Red Oak S/B 3-1/4 with DuraSeal Quick Coat Coffee Brown using a buffer & carpet pad, before he applied the stain he water popped the floor with a water mister, went back a day later, noticed there was blotches all over the floor, my answer was he did not water pop consistent. Is this correct? what is the solution?

Likely, water popping needs to be done consistent. Leaving any wood dry will result in lighter areas.
Just spritzing water on (droplets) will cause a leopard like appearance.

To do it right mist water on floor evenly so all is wet (not puddling) and immediately come back with a pad applicator (or T-bar if a professional) and pad off the floor removing excess and somewhat dry areas.

Sand it of and start over.

Johannes