I re-checked some announcements and it looks like the 135H will not become widespread for notebooks and mini-pcs. Most offer only the 155h and 125h. The 125h isn't that attractive though, because it only has 7 Xe graphics cores.
If I had to make a guess, then it would be that the 125H and 135H are both defective chips. Either with defective CPU or defective Graphics Core (compared to the 155h), and that Intel just disabled those parts of the chip and called it a day. Though I'm not entirely sure about that. But Nvidia also does the same to their lower end chips.
Fake-Edit: Just as I was writing this I made a google search about Intels i5 CPUs and people confirm that is exactly the way it was. At least with previous Intel CPUs. Not sure about the current one which is "tiled". But I guess it will be the same.