It was very nice :) I think subtext/yuri boundary stories can be tagged either way depending on the tagger - I only think the yuri tag is required if it is blatant (like they kiss or confess) - if it isn't then I don't mind a subtext tag even if I think it felt stronger than that.
In this story for example at the end it really felt like they were about to realise they loved each other.. I'd bet good money they became a couple not long after this :) But its still ok as subtext since it hasn't gone there yet.
I'll never not like QuietxGenki couples. Especially if its the quiet ones who are making the Genkis come to realize their gayness. Double points if the former themselves are oblivious while they are doing it. So this oneshot gets a gold star. Who cares if its not explicit, its just the right amount of fuzz