Its probably fair to assume this is just a loose note of how the Sea water restriction used to work in oda's mind logically speaking.

Calling all water "sea water" can't inherently be true because the properties of purified, condensed, boiled, etc etc is completely different from that of actual sea water.

Of course in the manga its a bit easier to avoid playing around with it, but im sure the anime has 'broken' these rules quite a lot. But i assume its just an overall loose rule. Because standing/purified/filter water is not the same as sea water. That would mean a whole mess of logic and plotholes could open up. like why hasn't the world government just solved the devil fruit user problem by submerging everyone belly down in regular water? Hose them down with a high pressure water hose until they submit or you cuff them with seastone?

It just would seem kind of stupid from a storytelling perspective if even regular water has the dampening/dizzying qualities a sea water bath would have on a normal devil fruit user.