I have read it thrice ...
And i still dont see what is supposed to be a problem. O_o
Its true that i didnt check if Divine Smite costs us Reaction ... or if Larian just put it there for covenience.
Maybe thats what you are talking about?
As for other smites, as far as i know (and feel free to corect me) they do cost Bonus action and cause Concentration ... but since they are delivered by Attack, Larian decided to merge it to single strike that costs both Action and Bonus action ... wich seems reasonable to me. O_o
//Edit:
I see i was wrong ... its not delivered by attack.
As i read
Searing smite for example ...
Its basically the same spell as Hex or Hunter's Mark ...
Wich makes Larian implementation even better since you cant forget to activate it.