I have a H4. I have no designs on a H5. I also have ATP helicopter/MEL. The reason I think the requirements to advance are strict is because unlike the rigid environment that we are in while achieving ATP, the environment for HG/PG is lax and unregulated, and it is appropriate to ensure that HGPG pilots are truly of the skill level that the rating indicates. If a rating allows one to fly from a site or fly a glider that they really shouldn’t then that affects us all relative to insurance issues.
The P2 pilots launching from Crestline with negative consequences is a bit of a low level example of the reasons for strict requirements for advancement.