It's about risk management. In this case they decided to take on the risk of account information leaking by not verifying the address instead of the risk to account conversions. The former shows more care toward their users and the latter shows more care to their bottom line. You can argue which is the right decision all day long but ultimately is a question of risk tolerance.

What's the point of a conversion funnel that creates exactly one conversion and then a huge amount of customer grief when they can never use the account again?

If the email address matters then validate it, if it doesn't need to be validated then don't ask for it.

I don’t understand what you mean by a “CF that creates exactly one conversion”.

Anyways, your response isn’t relevant in that I’m not suggesting an email address should (not) be verified. Rather, we’re discussing whether verifying identity needs to come before or after (or alongside) the transactional email - e.g. a receipt of purchase.

At the same time, validation and verification are not the same thing - and sometimes it’s not necessary to perform address/identity verification.