You could only be doing that if you think it’s true, and you would only think it’s true if you knew for sure that there was a reliable source, but you either forgot what it is or for some reason you didn’t want to give the real source.
Plus I would assume that it’s only permitted in a situation in which you feel that it’s really important to convince someone of this truth. For example, if people are being mevazeh Talmidei Chachamim and you know that according to the Torah that’s a terrible thing to do but you don’t have the source off-hand, and it is important to speak out right away.
I can’t imagine this would fall in that category, so I would find it hard to believe that you made this up. If you knew this was true but didn’t remember the source, you would have just said so.
In any case, it’s very interesting. Thank you for sharing.