In short, can Portal Lights use Cast Shadows?

I've been working on an interior set & think this is a good candidate to use Portal Lights. Went the Wiki, read the page & got the sample scenes. I start with the Teapots_PortalOFF & read the notes then moved on to the Teapots_PortalON scene. At first it looks normal & I select the Portal Light & Properties panel. I enabled the cast shadows & went back to the Basic tab. If you now toggle Portal, the scene goes black.

It's the Cast Shadows option. Enabled, scene goes black & renders black.

Since I've never worked with them before, is this bug or feature? I am using 2019.1.3.