I have no argument with Berowin's shield being different. It IS different. My argument is with the idea that the Forsaken use something like her shield. If so, it is remarkable that oth Nynaeve and Rand described shields woven by Moghedien and Lanfear as "walls" when trying to push against them.

The other side of this is that shielding a person while they are channeling isn't exactly the same as holding a shield on them. Do we think Berowin would have been able to cut off Nynaeve had she been channeling as much as she could?

We KNOW that landing a shield on a person channeling is a chancey thing. Nynaeve has told us that, and several of her scenes have demonstrated it. Which is why I'm skeptical that just because we've seen Aes Sedai land shields at some point, and not at others, we should ignore the evidence that their shields are similar to the Forsaken's.

Well Liandrin was blocked in some way. Suroth, as a non-channeler, doesn't necessarily have to use the word shield. In fact, we know the Forsaken use the word "buffer" for a shield, and we know the Seanchan call shields "blocks":

This is the Sul'dam Rand and Aviendha encounter in tFoH. She calls Aviendha's shield a block, so it seems reasonable to assume another Sul'dam/damane used similar terminology to descirbe Liandrin's shield to Suroth.