Same, they work fine and are immediate. The only exception has been Signal. Must be that I'm using sandboxed Google Play Services?
It is sometimes annoying to me. I cycle a lot and sometimes my wife or somebody else sends a message when I'm on the go (like picking up some extra groceries) and then I miss it.
There is a longer discussion with various people here:
So yeah, I can totally accept that this may be a thing.