The company that sold
you this product is correct. The 502 is the version sold
for commercial use in the RV repair and manufacturing industry. I have seen a comment saying it is slightly thinner than 501 which is sold
in RV supply stores to owners. Being slightly thinner would have the advantage of make it faster to gun out of the tube and easier to level but that would not effect its performance otherwise versus the 501 version. In the RV manufacturing and repair world speed and ease of application is important.
If I had received 502 instead of 501 and learned the difference between them then I would be a very pleased customer who felt they got lucky
I would feel lucky because sometimes these products are next to impossible for me to get out of the tube even using a high quality caulk gun. So to me something easier to gun and level, that otherwise gives the same performance, would be a real advantage. But it is up to you to decide for yourself to keep it or send it back.