Comments further down are concerned that on each page load, you're sending both the URL and a(n identifiable?) user ID to TBC. You may want to comment on that, since I think it's reasonable to say that those of us using not-Chrome (I don't use Arc personally, but I'm definitely in the 1% of browser users) are likely to also be the sort of person concerned with privacy. Vulnerabilities happen, but sending browsing data seems like a deliberate design choice.
I think that is addressed in the post. Apparently the URL was only sent under certain conditions and has since been addressed:
>We’ve fixed the issues with leaking your current website on navigation while you had the Boost editor open. We don’t log these requests anywhere, and if you didn’t have the Boosts editor open these requests were not made. Regardless this is against our privacy policy and should have never been in the product to begin with.
Given the context (boosts need to know the URL they apply to after all) this indeed was a "deliberate design choice" but not in the manner you appear to be suggesting. It's still very worrisome, I agree.