Every new ball seems to be advertised as gets more length and sharper move down lane . 7-10 splits are usually the result of the ball coming in slightly behind the head pin. While it may look like a strike from 60 ft away, it's not actually the flush pocket most bowlers claim it to be.

Does this mean the move would be to find a bit more oil, thus saving rotational energy....but not opening up angles (much) to prevent coming in behind the head pin? 

I had one ball a few years back...  loved the roll/reaction (at least to my eye), but left more 7-10's with it then I can remember with any other ball I've owned.  Nothing like shooting front 5, 7-10, next 3, then finish with another 7-10!
 

Does this mean the move would be to find a bit more oil, thus saving rotational energy....but not opening up angles (much) to prevent coming in behind the head pin? 

I had one ball a few years back...  loved the roll/reaction (at least to my eye), but left more 7-10's with it then I can remember with any other ball I've owned.  Nothing like shooting front 5, 7-10, next 3, then finish with another 7-10!
 

From the point of view of my eyes, many balls hook too much and burn up too much energy hooking and have nothing left by the time they to the "pocket". When you're lucky, you kick out the 5 and the 8 and leave the 10; when you're not lucky, your angle lets you kick out the 5/8 but you hit the head pin too light and the 2/4 wrap around the 7 and leave the 7-10 staring at you. Both balls used too much energy hooking and nothing left to "hit".

You need a tighter line or a little more ball speed, to allow the ball to save some of the energy you applied to it or you need a different ball with less flip.

Could be bad racks

First, a bit of history.  The pocket 7-10 was extremely uncommon prior to the mid 70's.  We started seeing it after the change from lacquer to urethane lane finish when they started oiling much shorter trying to combat carry down.  The split occurs because the ball creates too much entry angle for the amount of rotational energy remaining.  The ball still deflects, causing the weak 10, but the angle of deflection changes enough that the ball can still weakly take the 5 pin out, but not hard enough to get to the 7. 

If you think about it you seldom see a 7-10 on a longer flat pattern because you cant create enough entry angle.  I do think their has been a resurgence in the amount of 7-10s, probably due to several factors including strong asymmetrical cores that want to flip really hard coming off the end of the oil.  Also, I think the higher viscosity oils tend to maintain a wet dry look even when they carry down a bit.