Please enlighten me about these 'incredibly bulky walls' that SD Terrakion is 'hard pressed to break through'?
No I'm not picking on you, but last time I ran a damage calc, after SD this pokemon happened to 2HKO everything usable in OU (emphasis: yes, usable NOT viable) not named Golurk to whom it happens to 49.47% Damage at MINIMUM.
I'd say the same for Landorus but a few select pokemon like Celebi and Cresselia can actually wall it (provided it doesn't run horrible Coverage like sludge wave; so I'll give you that)
So please answer me.
If you reread his post, you'd see that he said "rather than" SD Terrakion. He said that the common Scarf Keldeo and RP Landorus are the ones that have trouble with the bulky walls, unlike Pokemon like SD Terrakion, and the fact that there are fewer SD Terrakion running around makes it that much easier for stall teams.