I think part of the issue is that these retailers are also customers of meta/google on the side of purchasing ads, and as a merchant you're highly encouraged to send as much data on your events as you can, or your conversion tracking can be "less accurate"and your campaigns are less efficient.

So it's less about "we're sending the data to $megacorp" and more about "I want the most bang for buck on my own campaigns" when the decision is made.

Using a different email certainly helps, though!

EDIT: highly encouraged by meta et. al! Whether this is a legitimate request to improve results or pure self-interest on the part of meta I don't know!