Roth Deducted from Gross or Net Pretax

Client is told from prior TPA that while they deduct pretax as a % of gross, they withhold Roth  based on Box 1 W2 (or at the least,  Gross - pretax 401k).

Per Document - definition of wages = wages, tips and other forms of compensation (W2 box 1)

Is this common?   Any thoughts or concerns I can advise on? 

15 minutes ago, legort69 said:

Is this common?

Not in my world.  Why on earth would anyone want to complicate things like that?!  Assuming it even says that in the document, which is unlikely.  

1 hour ago, Bird said:

Not in my world.  Why on earth would anyone want to complicate things like that?!  Assuming it even says that in the document, which is unlikely.  

Agreed.