While posts don't have any proven Local SEO benefits, they certainly help your business get the most of the traffic it receives.
Every so often Google updates the features available with their business listings. Last year we got expanded description text, websites, services, and more.
This year we get... Additional photos for GMB posts?
I'm not sure if this is an advantage yet, but I'm sure it will be useful for some businesses.
For most of our clients, unless we are including images from a past event, we will still likely only post a single image so it doesn't compete with itself.
There have been a few bugs reported with the new multi-image posts, have you seen any?