I would like to request a DDF for the Philips Hue GU10 Smart Spotlight White Ambiance (bluetooth enabled). You can find the github issue here: Philips Hue GU10 Smart Spotlight White Ambiance · Issue #7072 · dresden-elektronik/deconz-rest-plugin · GitHub
The device you listed is already usable out of the box. A DDF is not necessary.
Yes and no while most lights should already work also without a DDF it’s good to move them over to DDF. That way we can over time remove old C++ code and also get automatic documentation and compatibility list entries which are generated from the DDFs.
Related: In v2.20.0-beta Ebaauw made a quite large contributions to describe Hue lights via DDF much better than what the old default C++ code does.