Waiting room won't show video for SDK users

I recently enabled video through the Customize Waiting Room option on my account, explained in this article. Participants joining the meeting through native Zoom clients see the waiting room video just fine, but participants joining via mobile or web Zoom SDKs don’t see any video. Instead it just says “Meeting has not started”.

There is no mention in the docs of the web or Android SDKs not being able to handle videos in the waiting room. The Customize Waiting Room panel does say that users need to be on Zoom version 5.7.3 or later for video to work, and that version number refers to the native client, not the SDKs.

I’m wondering if I’m doing something wrong or if the docs simply haven’t been updated yet?