Cannot include siblings pages with a relative path using the page parameter

Steps to reproduce

1. Create two siblings pages Sandbox.A and Sandbox.B (terminal pages)
2. Write some content in Sandbox.A
3. Include Sandbox.A in Sandbox.B using this {{include page="../A"}}

Expected result

The content of Sandbox.A is included in Sandbox.B

Actual result

Nothing is shown in Sandbox.B

Note that {{include page="A"}} should probably also work (and doesn't) and {{include page="../../Sandbox/A"}} does works

Originally reported by @vpfar