Thanks for sharing the interview, truth be told I already had my issues with the current scale of Meliodas, being that it seems to me that his base should be stronger than what we currently have, as well as a couple of issues with True Magic which should be maybe 5-A.
For starters, as they posted above, Meliodas is the stronger sin, and if I remember correctly, that has been said in 4KOTA as well, plus the statement that he is superior to Arthur, there is no reason to think this is just with their multipliers, as during their matchup they were even, and there was no way there was a x4 difference even though neither of the 2 were giving it their all. Besides it was only when Tristan got in that he had to use the 2 mark, but this was because now in addition to fighting he had to protect his idiot son.
In addition there is the statement that he is superior to Lancelot who faced Arthur's base without complications.
Regarding the True Magic Form, (which by the way is written in his profile as "Possibly 5-C instead of the direct 5-C that has its base, this is curious) it is said in his profile: "Zeldris described his power as 'well beyond' Demon King, though which form he's referring to is unknown;"
But this is a bit strange, to begin with, supporting Zeldris' statement, we have that to destroy curses one must have a magic power at least at the level of the Deity and the King, And we have it to justify Merlin's level 5-C: Reactivated Elizabeth's resurrection curse, the creation and destruction of which requires power at least equal to Demon King and Supreme Deity.
This means that we accept that merlin's magical power must be similar to that of the deities for a feat that not only does TMF Meli also have, but also has supporting statements of being far superior to the Demon King.
Statement coming from a Zeldris who had just seen the magical power of his father by possessing Brittania.
Adding to all this, some time ago and if I remember correctly, the author stated that the magical power of Meliodas' TMF was close to the mother of chaos, who kept all the power of chaos.
For all this, Meliodas' base should go higher, at least Low 5-B as we have now to Arthur's base, and the True Magic Form should be at least Low 5-B being above the Demon King Brittania, and maybe 5-A, if I remember correctly the author's statements from years ago.
If I got something wrong tell me, but what do you think?