It can be true but I think it's important we don't state it as absolute fact.
Absuive relationships often start out feeling perfect. Absuive partners often lovebomb and adjust their personality to make someone feel completely understood and safe and happy. If we say 'you just know', someone in that situation might be less likely to think critically about the risk when it starts falling apart, thinking that they'd found this rare, important type of love and blaming themselves for it not being right.
On a practical level too it's a bit... magical thinking for me. Like it's some kind of psychic 'knowing' based on how fated you are to be together. And that ignores the practical aspects of a successful relationship that are equally, if not more, important than chemistry. I've had that insane chemistry, great connection, 'holy shit is this My Person TM' - with someone who, it turned out, had very different long-term goals to me. So he wasn't the perfect person, he was someone I had a great connection with, but practically speaking it wouldn't have worked.
Not long after I met DH I had a very strong feeling what we had was different - and almost a decade in, I'm still right. But it could change - we don't go into marriages or relationships thinking of the possible negatives because it's unromantic, but the person you think is the perfect person for you is still just a person who can and might change into something much less perfect.