I have two bows, one a Saxon American recurve 58" 57@28, and the other a BW 58" SAV 62@28.  I happily shot and hunted with the BW all season.  Picked the Saxon up last week and started shooting it again as I was thinking of selling it.  Big mistake.  Could not believe how much better I was shooting the Saxon.  I'm sure there are all kinds of mental excuses for the differences in accuracy (all my excuses are mental,anyway), but the question I'm throwing out is...just how much difference should five pounds of draw weight really make?   Five pounds is not a big deal at the gym, so should it matter that much between two bows?

Here's what I found...
I had to shoot my 45# bow since the limbs on my 57# bow broke a couple of weeks ago. Granted 12 pounds is more than five, but I noticed my T was much much better and my back tension was awesome. My theory is with all the work I put into form shooting my heavier bow that my form was that much better shooting my lighter bow, increasing my consistant accuracy.
So to answer...the lesser draw weight is making you shoot better because it is easier on you to shoot with better form.

5lbs will definitely feel lighter when you are used to shooting heavier.  If you go up 5 lbs it will feel heavy.

Also, if the Saxon has a longbow riser/grip and a longer working limb than the 58" BW, that could add to the lighter feeling.

5lbs makes a huge difference for me. I have two bows that are 5 appart. When I shoot the lighter one, I have much more control and shot placement.

Yep 5#'s is a lot....
I have been contimplating sending my HH Bow back to Jenny "Craig" to get a weight reduction....

I'm not getting any younger, and going to a 45# with a 30" draw made a big change in my shooting.Good Hunting Grant

I would think that the effect a five pound difference has would depend on how close the heavier weight was to your strength limits.  I shoot probably ten to fifteen pounds what I can comfortably pull over a session at the range.  So when I drop to a lower poundage it doesn't have much, if any, effect.