I took the "standard" maximum $22.5K + $7.5k deduction on Schedule 1, Line 16 for my solo 401(k). The program shows certain owe/refund amounts for Federal and State in the upper left. If I increase this amount to the Contribution Worksheet max to include Employer Matching (Profit Sharing) Contribution (let's say it's another $15k), the program doesn't change the owe/refund amount.
It would seem the owe/refund amounts must change if the employer contribution is before taxes. Otherwise, I'd be paying taxes twice on the employer-contribution amount, now and then down the road when I take RMDs on the solo 401(k). It is my understanding that all funds in 401(k) accounts are pre-tax.