As a long time motorcyclist I laugh at the idea of a water proof joint
As an ex- metallurgist I laugh at the whole idea of them for anything other than sensors that have very small voltages , like O2 sensors.
Metals corrode because they form a galvanic cell
For that to happen you just need two dissimilar metals to be touching each other while damp , the dampness completes the circuit .
So the supposedly waterproof joint lets moisture in and holds it there providing the perfect corrosion conditions.
The best thing by far is to grease the plugs with lanolin grease which you can get as a spray but I just melt it and dip the plugs into it .
You can use the expensive electrical contact grease but it is based on lanolin in any case .
Note I used the word dissimilar and not different .
And one of the things that makes metals dissimilar is cold working
So in the Packard type connector that seems to be favoured by US factories, the female being cold bent into a U shape at both sides will form a galvanic cell with the male which is stamped and not worked despite them both being the same grade of brass
The tubular Molex type is not worked as much so is less corrosion prone than the flat blade type .
