I have seen this happen quite often on wire spoke wheels. The water gets inside the rim through the holes where the spoke nipples go. The rim strip does not do a very good job of sealing things. This is especially true of dirt and dual sport bikes that are ridden through water. But the Elite has a solid rim, the only hole in it is for the valve stem. Since most motorcycle and scooter tubes use metal threaded stems with a nut inside, it's not completely waterproof, but should be pretty close. Also remember that the tire does not have a bead seal like on tubeless tires, and if the tire pressure were too low, or you used a high pressure washer on it, water could also get in between the tire and rim. Since there is no rim seal, you can still use the rims, unless they are rusted so badly they are structurally unsound.
2002 Vulcan 750 (now being slowly reassembled) 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped