I'm positive Trace was referencing JoMo. He has a right to be upset, they spent a lot of time together over the last two years and as a young kid you look up to your coach. PSU preaches loyalty, loving each other, brotherhood, etc. so not hearing it from your own coach hurts.
I will defend JoMo for this reason. He has probably been through a whirlwind few days this week. I don't know the exact circumstances or details of how it went down and the offer but by all accounts it seems to have happened very rapidly. It was only a couple of days since their last game of the year and JoMO was down to Miss, interview, make the biggest decision of his career, talk to family, perhaps other coaches/mentors and so on. So I get if he didn't have time (i doubt since he decided to go there he's been back to HV) or even an opportunity to address the team.
But I will say if true one would think he would have reached out to some at PSU, specifically Trace who he worked so closely with to say something. It takes under a minute to send a text or make a quick call. I know I would. Even a I'll call you when things settle down etc would be nice. As my mother would say when i was just a young boy, its common grace and courtesy. Unfortunately, not everyone was taught the same in life.
And I don't think its in any way a coincidence he sent out the latter tweet. If he hasn't specifically said anything to former players besides that tweet, well he's a jerk and I would take it as a slap in the face as well.