Your scales are tough to AC 13 ...
USUALY ... best AC calculation is used, so if you wield any armor that provides less than 13AC, then you still have 13AC
Normally that is the case, as we've chatted about in the other thread about AC... but many AC calculation methods have specific caveats that negate them - such as Monk's unarmoured defence, which is prohibited by shields as well as armour - or more pertinently, mage armour: Mage armour lets you calculate your AC as 13+Dex,
But only as long as you aren't wearing armour - so if you put on weaker armour, mage armour cannot function.
Sorcerer's draconic resilience has a similar caveat - It lets you calculate your AC as 13+Dex, but similar to mage armour, it only functions, specifically, while you aren't wearing armour, so, if you do wear armour, it is not able to be used to calculate your AC, which is why I think this poster brought it up, and why I suggested the in-universe explanation I did.
That said, I think that we would lose nothing and it would not be overpowered in the slightest if Sorcerer's draconic resilience did not have that caveat, and could function as a 'baseline' option at any time. It wouldn't hurt balance overmuch in this particular case.
