I guess in the end it's all about a companies culture and economically it boils down to "can I sell it". I want to add some random thoughts:
- Probably PHP wasn't your first language, you came from somewhere maybe Perl, maybe Java. There were reasons why you'ved switched.
- Is switching so hard? In my experience it is not! Good programmers are good programmers in every language. Get an expert to make your transition as smooth as possible.
- You do sell innovation - why not have an elite unit that can be with the new stuff. You can do 80% in your biz with stuff you know.
I get your point. The people I work with who know about "obscure techniques" are sometimes better UX designers than the people who don't know. That is because they actually know the barriers of what's doable in the browser. Living on this edge is not easy as all techniques evolve all the time.
When I talk with people I don't want them to recite these solutions. I want to see if they know their ressources.
For a user experience designer I would have a different interview.
What's important for me is to see if some understand what is happening behind the scenes. There are so many people who apply a clearfix but do not understand the principles of block contexts.