It took me a minute to realize that your comment was in the quote !
Yes you're right. And sometimes it's not that simple : multiple parameters are dependent on the instrument number being added or not and you can't choose which one you want to be carried on or not, they all are.
As always with trackers, there is a lot of control but a limited number of command in one row, so choices have to be made when complexity arise. That's why I like permanent channel commands that can be added here and there to modify the whole track (like Mxx, Xxx, Zxx, some sound control S9x commands, etc). S7x commands that deals with NNA or envelopes could have been permanents in the IT format, I would'nt have minded !
Off Topic (kinda) : I've just noted that for multi-sample instruments, when not adding the instrument number, the sample is no longer the last one used (like in modplug) but the correct sample mapped to the new note. That's a great correction !