I didn't look to the big guys, just made it up.

I did some digging in manuals: Keysight doesn't have a property like this in there list function in the models I looked up. The R&S NGP800 has an 'interpolate' option in there implementation of a list which they call ARB. It's not exactly defined what interpolation it does, but looks like lineair interpolation, which I called lineair ramp before. On there product page they have a screenshot of it (under Arbitrary Function):
https://www.rohde-schwarz.com/nl/product/ngp800-productstartpage_63493-670592.htmlThe word Interpolate/Interpolation is a much more specific description of the functionality compared to the TYPE I made up.
The R&S SCPI implementation is not so nice (to my taste), because you quickly get into some kind of comma-counting-hell

and it doesn't allow for adding options/features later on in a backwards compatible way:
ARB:BLOC:DATA 1,1,1,1,0,2,2,2,1,1,3,3,1,0 (its a repeat of volt, current,time,interpolate)
BB3 equivalent:
LIST:VOLT 1,2,3
LIST:CUR 1,2,3
LIST:DWEL 1,1,1
LIST:INTerpolate 0,1,0 (new, instead of TYPE, 0= step, 1= interpolate)
Both sets of commands do the same:
- 1V,1A for 1 sec as a step
- rising from 1V,1A to 2V,2A in 1 sec (this is the function we're talking about)
- 3V,3A for 1 sec as a step
I agree that more complex ways of interpolation (e.g. exponential) might be better handled with the ARB subsystem. Just adding the interpolation makes the list function very powerful (in my opinion).