It seems the English language is still mutating even as we speak. (Yes. I know I'm writing, but 'as we speak' is a figure-of-speech)
I just finished a book (no names, no pack drill) where a time-traveller went forward in time for about 900 years. Another character described this as time-travelling for almost a millennia.
Later another character is standing on the (decorated) tomb of Queen Isabella, but a few lines later is described as sitting on the sarcophagi. Now maybe he'd pushed two together to make a more comfortable seat, but I doubt it.

Sometimes I just gloss-over these things. Sometimes I gnash my teeth.

Even Mr Red's comment above: Let me see.............. what is said verbally? makes me edgy. Can we 'say' something non-verbally? If it is done verbally do we need 'said'?

As for 'walk through' I'd accept either pluralisation.
Walks through, pluralised in line with mothers-in-law and Aides-de-camp.
But also Walk throughs. Here we are not pluralising the 'through' but the whole compound noun (even if written as two words).

And BBCW: I would say that the walk-through is hyphenated and hence can be plural.
No! it can be pluralised. I don't think anyone else is claiming that 'walk-through' could be plural of itself.

Just my 120th of a pound ;)