Okay, the original wording is crap under the new rules (it used to be a roll rather than a tag/invoke). So I think this should be more about being effective with your holds, being able to hold them longer. A grapple counts as an attack-oriented action IMO (since a maintained grapple = the ability to inflict stress), so a +1 is appropriate here rather than a +2. My reword, then, is:
Wrestler: When maintaining a grapple (page 211), gain a +1 to your Might.