Making the pledges individually seems to make sense - I don't think long term support is something many startups can seriously offer and it feels like selling smoke to try to sell that in the typical case.
Making them retractable with user knowledge also seems fair - although retracting LTS just before shutting down isn't really meaningful.
I think really my concerns are probably just around LTS, which I think is really unrealistic for most startups to guarantee - and ultimately meaningless if they fail anyway. The other pledges just seem to make acquisitions/pivots less likely and thus shutting down more likely - screwing over the LTS pledge again.
I can see why it'd give some users confidence but ultimately at least with LTS it just seems to end up being a buzzword selling point with nothing really behind it.