Ck's post (the 2nd quoted) doesn't say anything about orphan rate or block propagation, his reasons are different, and he describes in detail: too little extra fee income, and the his worry about UTXO bloat.

The post about MARA mentions increased orphan block probability due to the lower propagation. This is quite interesting.

But look at the full picture:

- that was in a time when virtually ALL nodes filtered sub-1-fee transactions

- the extra income from these transactions is minuscule.

These conditions are not the same for the kind of spam transactions discussed!

(BTW, this post is more of an anecdotal evidence, but I credit it credibility.)