One of the reasons that I've given Belichick a lot of deference on this is because the memo misquoted the rule at the time.
The actual rule was "No video recording devices of any kind are permitted to be in use in the coaches’ booth, on the
field, or in the locker room during the game.” Coming from a b/r article, I've always understood the field distinction to be important because it is defined elsewhere as being the area between the sidelines. It would serve to prohibit cameras actually placed on players themselves. The rule also doesn't have that final sentence about locations available to club staff members.
Since the rules can't be changed with just a memo I've always seen it as more of Belichick reading it, seeing that it didn't quote the rule correctly (or knowing the rule and glossing over the differences in the memo) and disregarding it. In hindsight you obviously follow-up and get an answer as to what is going on, but it's not something you expect to lose a first round pick over.