Home and End seem to work like "PgUp all the way" and "PgDown all the way".
It seems Cmd+Left/Right is what I would interpret as Home/End.
What I'm learning about myself is that I actually do use Home/End a lot (often with Shift) to edit lines, but that muscle memory is out the window now.
I'm sure these semantics are useful for somebody, but I'm confused why we needed to have two different semantics for Home/End? Could we not have just made up different keys for the two operations and let keyboard makers put whichever they want for their layout? That would at least work consistently.