I read in one of the issues that it was Marketing that wanted Pendo tracking. (I'm guessing marketing mainly wanted it for gitlab.com).

In one place I saw a developer basically say Pendo is marketing's, and product is only interested in using Snowplow (with first party data processing).

Development was entirely happy with a true opt-in. Development does want to be able to get data back from on premises instances, but is totally fine with having it be an instance wide option that can be off.