Tip: Look for guitarists that either have been/are also drummers, or have experience as audio-engineers/producers. They'll be a lot more likely to have internal rhythm than people who have only played the guitar and nothing else.
I don't think that's any kind of absolute, though.
It all comes down to how you were trained (or how you trained yourself) to play.
Proper/traditional training will always focus heavily on timing, whether it's guitar, piano, sax, drums...etc.
There's absolutely no reason why guitar players would automatically have any less "internal rhythm"...unless they simply avoided the proper training and timing exercises.
Now you may be right on some level, simply due lots of young players not bothering to work on timing...and instead, all they focus on are licks, tricks and speed, and they just learn to copy shit note-for-note without thinking about the rhythmic context that they are playing in...but all music, all playing has a rhythmic/timing component, no matter what the instrument.
Not to mention...I've played with drummers who also can't keep time worth a shit....and they too call it "playing with feel" when you point out their poor timing.