Marko, thanks for the explanation but I want to clarify an issue I see in the case the aircraft is climbing in FLCH mode but has not YET reached the FLCH speed - if I set the FLCH to a certain speed it is indeed maintained by the aircraft pitch change HOWEVER once reaching the target altitude AND IF the aircraft has not reached the FLCH speed yet the auto-throttle changes to SPD mode and holds the current speed and not the target speed set initially (since the aircraft did not manage to accelerate to the target speed yet)
In the 737 for example in this case the auto-pilot will capture the altitude and the auto-throttle will change to SPD mode however the aircraft will speed up in ALT hold until reaching the target speed set initially and will maintain it.
I can post a video if needed.

Thanks