Would you prefer that he wait until after the acquisition closes and then have to fight a multi-billion dollar corporation and a newly minted billionaire cofounder? He obviously feels he is owed something, and strategically, it was now or never.
I cofounded a company, named it, was listed as the inventor on the company's patents, wrote its first product, had a written equity deal, and still got screwed on an acquisition like this. It wasn't for billions, but it was for more than $60 million. The acquirer was a multi-billion dollar company and once the deal was done (I didn't find out about the acquisition until after the fact) it was impossible for me to fight them.
I don't know what the merits of his case are, but looking at this from Jeremy's side, having been similarly positioned, he had no choice but to do this right now. Once GM has the company, unless Jeremy has some insanely wealthy backers willing to fund a very expensive legal fight for many years, all bets are off.