We use a part in our assemblies that has over 150 configs in it. When the part is added to an assembly the Engineer selects the correct config for that specific assembly. The configs are basically engraved labels so it varies per assembly and we create a few thousand assemblies per year.
We just upgraded from 2015 to 2018. When we open a 2015 assembly in 2018, the engraved label is wrong. We reported this to our distributor and they told us that the assembly is displaying the last saved config from the part model and not the config selected in the assembly. They also said that's the way it's designed to work. If we create a design in one version then open it in a newer version and it's different, to me that's a bug in the software.
For example, if we sent a 2015 design to a vendor that happens to have 2018, they will see a different model then our Engineers do.
Our VAR suggested rebuild all the configurations of the part model in 2018 before we convert the assembly to 2018. We will have to do this for thousands of assemblies. Also, once everything is rebuilt the part file is over 600 MB/