It's all pure physics. If you introduce a row of holes at the neutral axis of a beam, this effectively reduces the self weight of the beam... which makes the entire structure lighter... and then you have very complex maths to calculate what the size of the holes do to the strength and load bearing capacity of the beam. But most of the maths have been calculated for building construction, namely, supporting weight load from above. In a tennis racket, some of that load comes from impact (so, internally, when the strings pull and twist the frame inwards), or even from the very simple situation when you "tap" the frame on the ground reaching from a low volley (an external force).
But what the holes do by reducing weight/mass in the frame is reducing momentum at impact for the same speed of swing, i.e. with lower weight you have to swing faster to generate the same momentum at impact. And it is this momentum that you pass onto the incoming ball (some gets used up to stop the momentum of the incoming ball - which comes fast but it's a relatively light thing compared to the racketweight - and the rest is used to sent it back to the other side of the net).
What Prince have done is to realise that by making holes they've taken away mass so - for the same swingspeed - they've taken away momentum. By putting back "material" they've put back the weight they took off (basically, they're leading up the frame for you), so they've restored momentum.
Frankly, it's a big con. They first take weight away, launch a series of models, and make lots of bucks from us suckers. But some of us complain the rackets are muted and start tinkering with weights to restore the weight and feel. So now they launch a newer model, both with holes and extra weighting to get us back to square one. It reminds me of Microsoft, in the old days they "had to grow", so they launched a half-baked new version of Windows because they had announced it and were missing the deadline; but then they realised it had faults, so they launched Service Pack 1; but after a while there were still faults (some of them triggered by the first Pack), so they launched Service Pack 2 - they throw a patch to cure a problem triggered by the first patch, and so on, whereas in fact if they had got it right in the first instance you (the paying customer) wouldn't need to b*gger about with upgrades any further. Unfortunately, if you get it right first-time, your sales suffer as people don't see the need to buy flaky upgrades.
So, my take on Prince's 2009 "energy restoring" range is - they sold you a problem-creating, energy-reducing patch (the holes) first time round; they're are now selling you a second, problem-solving, energy-restoring patch. But it is "their" patch solution, and if you buy their new frames but their solution doesn't quite agree with the way you've been solving their momentum-stealing problem till now (with your own leading), then you'll have to go through yet another round of tinkering with weights on the new frames you buy to get back to the frame characteristics you want to play with. It's just not worth the trouble and money.
That's why people still talk about the classic POGs. I used those and loved them, but as soon as they were superceded and Prince went for NXGs (which I tried but didn't like), and then started drilling holes in frames and changing the holes every season, I moved to another make - which in turn did the same thing, n90s to k90s, etc. My coach uses Diablos, which haven't changed for years (no holes there), and has them custom-matched, which of course is a lot easier to do if the base stock frame doesn't change from season to season.
In my view, ideally you have to find a "classic" neutral frame that you like (weight, swingweight, balance, etc.) and will remain unchanged for years (or else you have to be prepared to buy a stock of frames). And then you customise them and change them as your game progresses. Which is another reason why pros don't change frames, they simply get the manufacturers to do PJs on the customised frames they have developed their game on - their personal molds.
