1810 why not send down more +5s?!

Level 252 is quite similar to 1810. On level 1810 there are hardly any +5s sent down, on level 252, once you get through the hard part plus fives are abundant (I know because I play this level a lot whenever there is a color challenge)....

While doing several (hundred;-)~ test runs, the average +5s while breaking blocks is 1-5, however when all blocks are broken through the average +5s are 0-1! Makes absolutely no sense, you would think once you got through all the blocks you would have more +5s!  There is no way to make it through this level without paying a butt load of money, which I don't have, and even if you did go through and paid 9 bars you still wouldn't be able to make it with that little amount of+5!!!