Cacheable xPages don't take into consideration shared uncacheable components

In a normal cacheable content page, if you add a uncacheable component to a shared container (header, footer), the page won't be cached.

If you do the same with a cacheable xPage, the uncacheable component will be cached. 

This is not intended behavior, according to https://xmdocumentation.bloomreach.com/library/concepts/request-handling/hst-page-caching.html

A composite tree of HST components is only cacheable if every HST component in the composite structure of components that will be rendered during the request is cacheable

Reproduction
Creating an x-page, making the mount cacheable and adding a uncacheable component to the shared header and footer container

Adding the same component to a normal content page works perfectly

See myproject14.7.7-cache.zip

/hst:myproject/hst:hosts/dev-localhost/localhost/hst:root/hst:cacheable=true
/hst:myproject/hst:configurations/myproject/hst:workspace/hst:containers/base/footer/slowComponent/hst:cacheable=false

• the SlowComponent in the footer is sleeping 3 seconds in the #doBeforeRender.
• page http://localhost:8080/site/content/sample-document.html is never cached, which is correct
• xpage http://localhost:8080/site/experiencepages/test-page.html is cached, which is not correct