Let me try to steer around this by using generalities and hopefully avoiding any breach of ToS, or at least being given a little leeway.
Tsem himself has been very clear. This forum knows that from past requests to him - the link has been given in the post preceding this one.
I have also spoken to a few Gelugpa Geshes about this.
In the NKT and out of it, no Guru has ever forced me to adopt any particular Protector practice, nor is there any samaya involved, as I understand it, with Gyalpos, either those approved of or disapproved of. So anyone is free to begin or end any practice their Guru recommends. Of course, if a being is regarded as a Yidam taking the form of a Gyalpo things may get complicated, but surely there would still be no samaya relating to that 'form' as opposed to the deity himself.
The Gurus I spoke to affirmed that we should focus on the enormous kindness and good qualities of all our Gurus in giving us Dharma practices.
None of the main parties (GKG ,Tsem Tulku and HHDL) has advised anyone to dump their Guru, and each is using a different Protector, oracle etc. so should be able to get along. However, Tsem Tulku is willing to act to do what is necessary to remain part of the Vajrayana which HHDL controls.
There is no problem with this, and the discussion of these three protagonists masks the really delicate issue facing those monks in India who are able to be disciplined by HHDL and their monasteries if they do not wish to abandon a practice when he asks them to do so.
Leaving aside propaganda and politics which continue to be problematic, most of those unwilling monks (all?) are now in monasteries where they are free to choose whatever Gyalpo they wish.
So this is an issue which is petering out and maybe we should pray that it fades to the extent that ToS are not necessary here.