I wouldn't take it so hard.

I can totally see something like this happening just as a quirky thing - kind of similar to how Chinese parents sometimes (or at least used to) disparage their kids, that are doing really well. Inside, they're very proud, but on the outside, they don't want to presume.

As a kind of "gesture to the gods", in that you're not 100% counting on this good fortune of your son's marriage, which would make you more vulnerable.