For the sake of simplicity, we will assume that you are not cherry-picking blocks that suit your theory, and let's just assume by mining empty blocks you save 150ms (75% of the whole process you mentioned).

Now since this happens almost every 10 mins, then that is A LOT of money to be made by mining empty blocks, and here is how.

There is 86400000 in a day, and 144 blocks to be mined, so by utilizing 100ms every 10 mins you get a total of 14400ms which is 0.0167% of the total 24 hours, in other words, Kano pool wastes 0.0167% of it's hashrate by not mining empty blocks.

When a pool like F2pool saves 150ms for every potential block, that's 552510 terahash worth of mining, if that's hard to understand think of it this way.

When F2pool knows about a new block coming, and while going through that 150ms process they switch their hashrate to another PPS pool and say that is Viabtc, by the end of the day they would get paid $1500 from mining for 150ms every 10 mins or a total of 21.1 seconds with 22,100,420.00 worth of power.

And it gets even better when you don't have to download the block in the first place when your pool is synced with the other pools via any other protocol and all you need is their hash (not even the block header) then that makes it well above 200ms, but even with these numbers F2pool can potentially make over half a million dollar in profit yearly, or otherwise, lose it if they use your code and not mine empty blocks.