Mega Reuniclus and Mega Magcargo's stat spread

Why add 50 points to Mega Reuniclus’ Speed when it automatically sets up Trick Room with Speed Swap anyway? Those 50 points would be more useful on literally any other stat. Also, lowering its Defense, even though it was only by 10 points, doesn’t do it any favours since those 10 points aren’t benefiting it in any other stat.

Why cut down Mega Magcargo’s Defense by 110 points if you’re only going to put 20 of those extra points into its other stats? Sacrificing its Rock typing and so much of its durability gave it no benefits beyond Vaporisation (which, unlike Speed Swap, has nothing to do with its stats) despite Mega Evolution granting it a massive total of 210 stat points it could be using.

The 50 points to speed for Reuniclus was done in order to balance it out. A mega evolution that freely sets up Trick Room without have to use a move, combined with it’s high special attack, would make it too powerful with its original low base speed. This way, slower type pokemon can be used as a counter to it.

With Magcargo, all I can say is that it makes thematic sense when you take into consideration that it loses its shell on mega evolving (hence losing a significant amount of defense).