OK, forced pushed to use same tooltip as other buttons.
Good to go.
(I've tested using this with hydrogen, and hydrogen and battle weapons in the cargo hold)

why the tooltips are passed as arguments to this function?

I am not sure why the original tooltips were passed in but makes sense a bit for re-usability.

mt purpose of adding the new tooltips was so that people could disable these buttons.

ie

slider(0 100, "down", "up") would be as it is now

slider(0 100, "down", "up", "min", "max") would show both and you could do

slider(0 100, "down", "up", nil, "max") this to only show the one button

Not obvious to me why the tooltips are passed as arguments to this function?

Because it leaves open the possibility for more specific tooltips like "increase scan frequency" or "shrink garbage compactor". Anything that's not passed as an argument is hardcoded to a specific value.
Another side-benefit is the transfer_buttons function can be copy-pasted into another file with less work.