Especially given that Heighten Spell also uses the singular ("saving throw") while clearly also including spells which force more than one saving throw (because it affects only the first such saving throw).
Did they? Who got fired?
I know Rodney Thompson left in 2015 but leaving != fired. I do regret his departure though because not only was he lead the lead of player mechanics design (per his 2013 resume anyway) but from he seemed to have pretty good design sense, from what I can tell of his talks and writings (see video in my .sig).
Were there other folks who left around the same time?