I don’t think there’s an objective answer for this.
To some people, “anyone does anything with an account that isn’t specifically theirs” is cheating. To some people, this case will cross a line because they might support account sharing, but they don’t like the idea of a player with a different skill level using the account competitively.
Personally, I think if one person wanted to create 30 accounts and run their entire guild, more power to them. I think that’d put the person at a severe disadvantage, because dividing your attention means individual accounts progress slower. (I also think trying to play GW with 30 unique accounts daily wouldn’t be worth it.)
I feel like that’s analagous here. If another person plays your account, it’s like your account is an alt of theirs.
To me, “cheating” happens when you gain some kind of unfair advantage. I think this isn’t “unfair” because the player using your account still has to use the teams/troops you have. It’s not like they get to bring things over and get points you wouldn’t get if you played yourself.
I think some people would say “the advantage is unfair because the guild ‘should be’ short a player and isn’t”. I don’t think I can find a way with logic to prove they’re wrong, but I also don’t think they can use logic to prove they are right. Instead, I think both of our opinions “make sense” subjectively, and you should do what your heart says.