You know you can't verify an incomplete block, right? If you think you can just plow ahead after getting the first packet... you are going to have a really bad day once the other miners notice that you can be fooled into wasting hash power on bogus headers. You know that blocks get announced by the miners after they solve the hash, in chunks that can be up to the max blocksize, right? For Bitcoin that is 1MB, for bcash it is 32MB. Imagine if NASDAQ offered two levels of service: one that put the FIX protocol behind a 1MB buffer, and the other behind a 32MB buffer - which one would be disadvantaged? Anyone sitting at the 32MB buffer would be getting their lunch eaten. This is about as fundamental as it gets, so you might want to do some reading - because you've clearly got a big blindspot.
> No they don't. The examples you are talking about are rare and have very little impact.
If you are talking about bitcoin, you are very wrong - it is a thoroughly documented occurrence, it even has a name: the selfish miner strategy. If you are talking about bcash, I dunno one way or the other - I don't pay much attention to the joke coins. https://doi.org/10.1109/ICBC48266.2020.9169436
> How long do you think it takes to send around 900KB ?
Again, you need to actually do some reading on how mining works and what the network propagation characteristics are. I really don't want to have this come off as meanspirited, but it needs to be said: you obviously thought you knew how things worked, and you obviously don't - I wonder how many people you've misinformed.