The Victoria and Krystal arguments don't go with your above argument since that leans more towards the why f(x) didn't make a comeback after 4 Walls and not why f(x) didn't tour much in their entire career.I'm inclined to go with Rand on this one.
It's seems very unlikely to me SM would have a group that was intended to be non commercial.
The resources and effort required to sustain a group would be hard to justify to corporate boards if there was not a articulated strategy for profit generation and pursuit.
The outside chance I see for the "experimental" argument would be if FX were someone high up's (like Sooman himselfs) passion project. Even then, a "pure research" project seems hard to get past a corporate board.
STATION fares better as a possible project with less monetary focus as you'd be able to argue it develops your artists and offers them an less expensive to produce and release outlet for artists the company doesn't want to provide large scale investment backing to. That can be justified to a board. An entire group seems much harder.
To me the likey explanation for FX and their lack of full scale advancement is there being some internal reason that the group wasn't pushed.
Having your leader in China not interested in or needing your group (Victoria) plus having your de facto visual and public darling not likey needing the group due to having other projects and attention outside the group (Krystal) seems a recipe for stalling a group. Having two key members that have other pursuits is a hard scenario within which to full push a group. (Not to mention the addition of Sulli's departure).
I'd argue EXO is a different animal as they had a larger number of central members with which to fall back on. Not having the full participation of two prominent members would have a much more paralyzing effect on FX in my assessment.
Anyway, we'll need a SM insider to write a book to really know for sure.
As for your EXO argument it depends largely on whether Krystal did not want to participate as she did participate in the f(x) performance at SM Town so I don't see why she wouldn't have done a comeback which Luna, Amber and Krystal would have been fine as a trio or some makeshift sub-unit like Oh!GG.
You are taking it too much at face value, SM experimenting isn't just like "oo let's see what this does" it's their way of innovating and leading the industry so justifying a group would be more along the lines of "we believe that blah blah is the future and we are going to use group to embody that" which SM have a track record for doing that stuff so hard to argue.
As for resources and effort while that would be true for some companies it's not really true for SM since their groups pay for themselves as even NCT have good physicals with like 100-300k depending on the unit so I think if one thing SM won't lose money with is their own groups.
Finally for Station most releases are just digital I think and nowadays they don't chart anywhere close to being a success so unless SM are using it to recycle songs they decided not to use for comebacks or self produced ones it comes across as a bad investment.