I have previously used Namecheap and not had this issue. I feel like if they were selling my data, I would have gotten at least one piece of spam at namecheap.m

I have previously used Namecheap and not had this issue. I feel like if they were selling my data, I would have gotten at least one piece of spam at namecheap.mydomainname@my-catchall-email-domain.com, which I never have. Although it's possible that there was a data breach, or even that they purchased the data from the payment provider you use. It's also possible they just lied to you.