Well then you hit the issue that in your blanket rule, you're limiting the character in other ways. For example, against falco. The ledge and/or below the stage is an incredibly advantaged position for MK. Even though it isn't really stalling, you're removing the strategy of "stay around the ledge, abusing the ability to be below the stage a lot against falco" from Metaknight, more or less. An unfortunate side-effect, but this is a ban you can't really do effectively.
Pretty sure that limits MK less than an outright ban lmao. Seriously it's way better to have a ledge grab limit to stop MK from breaking the rules and make some of his options weaker than ban MK.
The MBR Ruleset doesn't have rules against rising pound or peach bomber stalling either. Not any more.
But it does suggest a stalling rule and rising pound is generally accepted as stalling as you CAN'T hit Jiggs.
Regardless it makes the game unplayable. He is at a position where he can never, ever, ever be touched, and its sole purpose is to time someone out.
It's as much stalling as using IDC (with more room for error) is.
He is as unhittable as pretty much everything we've ever banned for stalling (IDC, CGs past 300% (which is unnecessarily limiting characters who don't need limitations at all), Jiggs' Rising pound).
I don't see anything that shows it as anything other than stalling to use the SBR definition. You cannot touch him any more than you can't touch Jiggs Rising Pound stalling in Melee.
Most tournaments in Melee have a rule for stalling that mentions Jiggs rising pound (SBR suggests such a rule as Jiggs' rising pound is considered stalling). For instance look at Pound 4 ruleset: "•Controller Mods, Glitches (IC Freeze Glitch, Mewtwo Soul Stunner, etc), and tactics used to stall a match (wall-bombing, rising pound), are banned."