This is true. You can break down the block simply with the jab, straight, jab, straight combination, then mix in a head kick, overhand, or modified strike and you can pretty much KO your opponent or drain their head health. You could repeat this process just a few times to get a KO off of a high blocker. If you use Stephen Thompson, he has a really FAST jab straight animation, so just spam that combo with him then go for a head kick and boom you win. Timing is important obviously.
Or choose Daniel Cormier, throw a 4-piece mixing in hooks and uppercuts. If you're using a lesser fighter like Jimi Manuwa the high block won't be able to absorb too much damage. A 4-piece combo by Cormier will be just enough to break down the block, then repeat the same combo and you can KO your opponent. If you try to counter in between the 4-piece you get stopped by the punches already coming your way, if you use head movement you lean into a punch and get rocked anyway. Your only defensive option at that point is to lunge and pray.
Edit: I just realized I posted this same post in two different threads thinking my previous post magically disappeared, my bad!

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