The devs quite literally do not understand how to play healers in their own combat design. It's quite embarrassing but not shocking.

It's been this way for the longest time.

WHM is being held back on purpose bc they want it to be the easiest possible healer to play. That means it cannot have ANY semblance of thought process, no complicated abilities or too many buttons. The devs think that WHM has to be the entry healer for anyone new to the role.

Which is super ironic bc of WHM's GCD design, it prepares nothing for the other healers who are vastly superior to WHM in terms of kit design. And unfortunately due to it being the classic healer of the franchise, it will always remain as the most popular. And popularity tells the devs that it needs no changes.