Obviously, IntelliJ IDEA is a polyglot environment so certain things cater to the needs of many platforms and languages, which is why there are some differences in UI, but AFAIK, the core functionality is there.
Having said that, we fully understand that users want to have smaller more focused IDE's based on the specific needs, which is one of the main reasons we started offer the All Products option.
But I do want to stress that the functionality of the different IDE's are via plugins, and that these plugins are available for IntelliJ IDEA, the same day the IDE's are released.
I'm very happy for the universal license, thank you so much for adding it. I love the special editors like WebStorm and PyCharm, and I use IntelliJ IDEA as well. I use them all, regularly.