Come to think of it, it does make an uncomfortable amount of sense. Tencent is one of the biggest E-Sports drivers out there (running the LPL, the Chinese pro LoL league, for example, while providing funds for Riot to run the other LoL regions and Worlds). If Nintendo ever wants to learn how to run such an E-sports scene, Tencent and Valve are probably the biggest options they could look at.
It doesn't affect how likely LoL is much if at all, mind (hell, all in all I still see LoL as an outsider at best, the leak feels really wonky and too dependent on factors going its way for it to be trustworthy. At least how things stands at the moment.). While I've long suspected that Nintendo's partnership with Tencent is more multifaceted than just "Switch getting an official Chinese release" Smash is not neccessarily part of the deal. Thing is, Smash could easily fit in those plans too. The timing (what with an abridged LoL - Wild Rift - probably heading to the Switch in 2021) feels a bit too convinient too.
Of course, this could wind up being nothing in the end.
Organizational culture is, if I may behave like
Cutie Gwen
for a bit, a *****.
I suspect that that line of thinking comes from years of Nintendo self-publishing its own games and consoles. "This is our territory / property, and
we pride ourselves on being exclusive!" Not every Nintendo employee thinks like this of course - but if an organization is successful at one thing (which Nintendo is) thinking like this spreads really easily within the organization (especially higher-ups). The key to success in this case lays within the whole exclusivity package.
There's the flipside though as you mentioned: Nintendo overreacting on a YT channel - or fangame - based on the mere possibility that said exclusitivy gets "dilluted". Organizational culture can wind up in some really weird leaps of logic.