I saw that post a long time ago and it pissed me off. How ironic that royai shippers, the ones who most adamantly insist that Roy and Riza are brilliant in-depth characters, are also the ones to horribly water them down to the point of “they only think about each other all the time in every scene, nothing else crosses their minds ever!!”
There is no subtext in this scene. It isn’t even a scene about Riza or Roy, it’s a scene about King Bradley and his remaining scraps of humanity. Riza is caught off guard by his comment because since finding out that both he and Selim were homunculi, she stopped seeing them as human and instead just assumed them to be intimidating monsters who looked down on all of humanity. The idea that Bradley could still experience love and could genuinely care about his wife – who was the ONLY aspect in his entire life that he had any choice in – is what caught her off guard. It made her feel uncomfortable because she realised that it wasn’t as easy to categorise Bradley as an evil homunculus because he was still human at his core.
(I should also note that I love this scene because Bradley/Mrs Bradley is one of my OTPs and it irritates me to see royai fans being like “this scene is about MY ship!!”)
One more point I want to make is that the scene in which King Bradley talks about Mrs Bradley in this way is very similar to a later scene in which Pride talks about her as well (this is just the tail end of the scene):
Alphonse’s reaction to Pride’s story is almost identical to Riza’s reaction; dumbfounded silence as they are caught off-guard by the sympathy they suddenly feel for the homunculi.
In short, don’t let it bug you. Both of these scenes are scenes about the Bradleys and their weird family dynamic, as well as the blurred line between human and homunculus. There is no hidden subtext whatsoever.