Prior to the introduction of the Timeline view, which I don’t use, Photo libraries had Grid, List, and Summary views, just like other library types. If you have entered a Summary for your Photo galleries, the Summary view is the only place that summary can be seen by the user. What sense does it make to take away the only method of viewing the summary?
As it turns out, the summary is also displayed when you view the image full-size (a fact I pointed out to someone else in the past, but conveniently forgot today).
Still, I think the Summary alternative to Grid view, at least, would still be a welcome addition.
Please restore the Summary and List views to Photo libraries when not using Timeline.