Worker routes not working for domain pointing at Kinsta

We have a subdomain name A in Cloudflare which is pointing at a Kinsta Wordpress site.

We have another subdomain name B that points to a different service not hosted on Kinsta.

If I enable proxying (orange cloud) on both in Cloudflare and add a worker route that matches a subpath, then the worker route works for domain B but not A.

I found this question: Worker route not working
where they mention that if the host is a Cloudflare Saas Partner, then they have control over it.

Is this the case for Kinsta webpages?