Rather not clearly phrased by me (english is only the 3rd best language of mine) so I'll do my best now to clarify: my usage of "as I understand it" was directed towards "case of" writing about a topic unknown to the author in general and not towards "detailed bits of 50 S".
As the discussion about said book on MR pointed to a great source of reviews and some pointed out an ignorant treating of the topic (e.g. examples of unsecure uses of aids commonly used in BDSM play) I took this as 3rd person (reviever) proven not needed to be discussed again.
Insofar I admit that I should have added "As reported by reviewers" were I addressing this point in particular.
Rereading my post I should have written "As far as I understand, it's a case of (...) as pointed out in several reviews" Please accept excuses and correction.
Unfortunately I omitted focusing my response on
The point I wanted to make was that, because BDSM as such is reality excuses from research based on the plot's fictional character didn't apply.