Sure, I could be overstating the case here. The main issue is we know that the script was originally written with Vader not being Luke’s father, and very explicitly trying to kill Luke on Hoth. Later, during subsequent rewrites, Vader was turned into Luke’s father, but he still seems to want to kill Luke on Hoth. It’s pretty hard to interpret the dialogue between Vader and Piett any other way than that Vader had planned on killing all the rebels via orbital bombardment, and only resorted to a ground invasion because of the shield. I guess you’re right that the dialogue leaves some wiggle room here, but not much in my opinion. (I mean the entire first movie was about blowing up a secret rebel base from orbit - so the audience would naturally assume the same idea in ESB.)
It’s valid to have these assumptions/expectations, but similar to what you’ve said, the whole function of these context-redefining plot twists is to throw our assumptions on their head. We the audience are obligated to see events in this new light so long as there’s any room to do so (I suppose our argument is over just how much room there is).
Consider - I never had the impression that Vader’s plan was to just blow the base up. Before they’re even on their way to Hoth, Vader specifically tells General Veers (General being an army or marine rank) “prepare your men,” which right off the bat has me envisioning an occupation. Later, Veers brings up a hypothetical “orbital bombardment” unprompted, in the context of the shield’s strength - his message is “Hey, the Rebels already have a big ass shield up and it’s REALLY strong, we won’t be able to battering ram our way through it.” And finally, when they actually do bring the shield down, Vader follows up by landing there himself. True, circumstances have changed by that point, but it feels incongruous if the ultimate goal was to simply wipe the base out.
(Also, this might just be me, but it’s a space opera convention that space weapons are flashy but puny, in order to facilitate lengthy and spectacular pew-pew battle scenes, so I tend not to presume anyone can just nuke-the-site-from-orbit-it’s-the-only-way-to-be-sure unless they specifically tell us, even if logically you’d think they should be able to!)