I think it is fine as long as you got paid full salary

Even if uscis questions your h1 in this circumstances, as long as you are paid full-salary as stated on LCA by both companies, there will not be any problem with you.
uscis is only concerned whether yoru H1 is true and valid, and they measure it by the money the company pays you. If you get paid, they don't care how much work you do for the company.