This is a known problem and I'm afraid I don't have an easy solution for that right now.
The problem is that a separate index must first be built to assign all related tags to job listings as some don't have any and others don't have all related ones.
Once that is completed, the search functionality will be reverted to what it was initially with the ability to search by strings and/or tech tags individually.
I've been contemplating how I'm going to achieve this for a couple weeks and have a pretty good model in mind but no ETA on when it will be implemented.