YZF parent
When those experts are not named one could wonder if they even exist. Why would a journalist not reveal the name of an expert who is consulting on a matter of law?
Not to get super conspiratorial, but I think this is almost certainly a weasel statement simply to avoid directly accusing Israel/google/amazon of breaking the law.
I can't imagine any "legal expert" dumb enough to say you can violate a gag order if you use numbers instead of words.
In all likelihood there's just language like "to the extent permitted by law", which The Guardian isn't telling us about. Even if they didn't write that explicitly, it's implied anyway - Israel knows any US court would void any provision requiring Google/Amazon to commit criminal acts (illegality doctrine). It's also not really possible for Israel to be break laws of foreign states, since it's not bound by them in the first place.