;) I was a by-invitation-beta in 2004, trust me. Even then spammers knew about the +1234 trick too. The earliest throwaway forwarders suffered from explosive growth and spam netblocks and their queue times varied greatly. The golden age of Viagra and recruiters selling prospect lists to randos. I retreated to gmail for the SPOP and because my original address was Tech Contact for 100+ domains from 1994-2000. Thousands a week. If I was smart I'd have used it as a honeypot to feed a spam blocking service.

Don't you get these spam mails either way ?

I have a separate email I only use to get government and public services (gas, electricity) stuff and it still receives a few hundreds of spam a week. At this point I kinda feel whitelisting the mail I want to read is the only sane option, so getting hundreds or thousands of spam mail makes little difference, while managing a portofolio of addresses is a chore.