Yes, this, and the fact that supposedly Randy wanted to "spend more time with his family", which must have been a totally incomprehensible sentiment to Don, Glenn and Timothy in the 70s, is probably another reason. They never had to worry that TBS wouldn't sing his songs or wouldn't put touring with the Eagles first. Same with Joe. They knew they could count on Timothy to commit, 100%.
I would be surprised to know that Randy was actually formally invited to perform on the HOTE tour, for many reasons. There's a difference between not holding any grudge against him and actually opening the show up to him being part of it. Has Glenn or Don said they invited him to perform? Or did they invite him to attend the concerts?