When I first saw this I got a spotted flycatcher impression. I feel the other 2 have a squatter, rounder feel than this. The long primary projection points that way too (despite the presumed brown staining).
Unfortunately the ebird resources for immature stages of the other 2 aren't great, but what there is is quite different.
I think AGF can be ruled out on leg colour, bill shape, primary projection and lack of supercillium, whilst PF can be excluded on bill shape and the density of streaking on the chest. I can't really recall seeing immatures of either species though, I'd have to check my notes.
Interesting - and obviously the books' depictions of these plumages may well be duff. On the other hand, these are also the types of plumage that might easily be prone to misidentification in photos.
Primary-projection in the OP's bird does, however, look distinctly better for spotted flycatcher than for African grey flycatcher or pale flycatcher - so I'm happy that's what it is.