I agree with Long_horn. Let me give you an example. H4 Visa are not allowed to work but recently USCIS is giving H4-EAD to the people who meets USCIS criteria if I-140 has been approved. Now, would you say why are you working on H4 for those with EAD? Same applies to TPS once you are granted EAD you can use that. It won't violate your status. You will be in H4 status even if you use EAD if the primary applicant (H1B) is maintaining his/ her status which means following all H1B regulations even if he/she has applied for TPS. Same scenario apply for F1 too.