I don't think this will change:

https://support.google.com/a/answer/6166309#slides&slides_error150&zippy=%2Cslides%2Cerror-or-embedd...
This is a quote from a different site I follow, and I think it makes sense: "This is about content creators wanting to be (rightfully) compensated for their work. When the videos are embedded, they don't show ads, which doesn't make money for the person who created the content." (Carl Sundermann on the Amplified IT collab site)
BEST SUGGESTED workaround I've seen: set the slides to 'Anyone with the link' / copy and paste into incognito tab / all embedded videos play. My understanding is that this is because non-education Google accounts do not experience this same issue. I tested this solution and it worked. I hate, however, recommending it because doing this 'denies compensation' to the YouTube content creator.