For the most part, the series
tries to stay true to scale.
For instance: Bowser.
In Sm4sh, Bowser is finally his official size.
Yes, Bowser has an official size. A few years back, Nintendo released a couple size charts of Mario characters. Showing that Bowser was roughly twice the size of Mario. Whether or not it was consistent did not matter, the chart showed how big Bowser
typically is.
So no matter how big or small Bowser became in his series, you couldn't use Bowser's size changes to argue for Ridley's chances. After all, much of the Mario series revolves around the gameplay of
growing and shrinking; a mechanic which Metroid does not share.
Which is why is was always weird for Ridley supporters to support him shrinking.
But, for this picture, it seems to me that he's implying that
there ARE exceptions. I know Ganondorf was shrunk, but his size change went mostly unnoticed by both the Smash and Zelda community. (Ganondorf is pretty much twice Link's height, as Link only comes up to his waist)
But for Ridley, the size difference would be much more extreme.
If you Ridley supporters can
truly support a size change of that magnitude... Well, you might just have a space dragon yet.