Not that wierd at all, Pete -- deads and squats involve some of the largest muscle groups in ways that presses don't quite as much (they do, just not at the same level as a squat or deadlift). As such, it makes total sense to me that you can add weight more rapidly those those lifts than to any kind of press.
I've been lifting since November 2007. I've been lifting moderately seriously since right around January 2008 (ish). Biggest gains were definitely in leg/back stuff ... e.g., I was pulling 315 x 3 on deadlift by April 2008. I didn't break 135 on bench *consistently* until July ... and that was on a Smith. Didn't break it consistently on a real bench until September or October -- just in time for me to hurt myself. Now that I'm better, I'm finally seeing my first noticeable gains on bench, overhead presses, etc.
Anyway, I'm not entirely sure what my point is.
I guess just that what you're describing makes sense and you can eventually expect to see other gains as you work on things. Not sure what finally made things click for me. Still trying to figure that out.
