Look, from what information is out there at the present, Huggins doesn't have a keg to sit on.
His resignation is/was official. Regardless of who wrote the resignation letter, it was presented by Huggins. Meetings were held in which HE attended. His players were told by HIM. They went into the portal knowing it was official - from Huggins and the university. Huggins said nothing for nearly 3 weeks as far as believing he was still the coach at WVU. All the while the players he recruited entered the portal and signed with other schools. All the while, sitting back and allowing WVU to go through a hiring search.
The university is free and clear in this. They still owe him what he is due for THIS year, so unless they are refusing to pay, refusing to pay in whole, refusing to pay on time, or something along those lines there is nothing to it.
As such, its hard to see what Huggins' angle is here. Is this a legitimate ploy to try to get his job back? Is this a ploy to get a chance to be rehired next year? Is this a ploy to get the university to cough up more money? Until we see the details of his suit and the codes behind it it is all speculation at this point.