Side-effect: You can mine absurdly large blocks and DOS everyone. Absurdly high orphan rates are just the cherry on top of the cake.
That is your theory.
I would say that miners have no incentive to allow absurdly large blocks or to engage in behavior that promotes high orphan rates.
That's the whole point of POW. It makes attacking the network exponentially more difficult and expensive than sending a few
thousand transactions through.
There is no theory. These are facts. You don't even understand why Bitcoin has the 'low' orphan rates today. You are also viewing this completely wrong. Let's assume all the miners are being honest (which is a very bad assumption). They have two options:
1) Produce much bigger, yet non-absurdly large blocks -> this solves nothing; spamming is a bit less trivial; mempool is still flooded with spam.
2) Produce absurdly large blocks to minimize mempool size -> high orphan risk, DoS.
A side effect of this is mining centralization as well. You are left with practically an 'ultimatum'; solve nothing & bloat the chain with bigger blocks or solve the problem but practically DoS everyone and risk with higher orphan rates.
Interesting.
All tx paying 0.0001btc fee,
All are straight into a block - no waiting, (are they even in the mempool numbers?)
All blocks found by bitfury.
Bitfury was recently testing out how to include the most number of transactions per block. Considering that these transactions aren't large in size, it is no surprise that they've been mining them.