Is the song Some Day Baby by Ray Charles considered a blues song? I think it is because I'm pretty sure it contains the blues progression I-IV-I-V-IV-I. However, it uses the note E natural quite a lot, which I think is unexpected for a blues song written in C major. You would expect it to contain E flat, because that's part of the blues scale for C major.
I would say it's definitely a blues.
The chord progression is a typical blues progression, as you say. The melody as well. It also has a typical "boogie" pattern in the left hand, and the typical blues "turnaround" (the last two bars of every chorus). Granted, it is not a 12 bar blues with the classic repeat of the first line (AAB form), but the 8 bar blues is a common variation.
(Of course blues can mean a lot of different things depending on who you ask or where or when. I would say this is the case for most genres of music or artistic expression, though.)
So apparently Some Day Baby is actually a rendition of Big Maceo's Worried Life Blues. If you listen to both songs, you can hear that they're very similar. Since Worried Life Blues literally has the word blues in the title, I think it's safe to assume that Some Day Baby is a blues song. I suppose blues songs are defined by more than just their chord progression or the scales they contain.