How do you know the address you’re emailing belongs to a business? The head of A&A ISP in the UK used to regularly win ~£100 judgements in small claims from spammers because his personal email was leased for a nominal fee from aa.net.uk, the same domain as his business.
If your email is used as a contact on Business subscription it is safe to assume that it is used for business purposes.
I mean that's cute and all, but it's a party trick, and very unlikely it caused any actual behaviour to change.
OP had checked that they would like to receive the "Proton for Business newsletter", and on that basis was deemed a "business".