I think you're not getting a response because the question is a little confusing.
As I understand it, you have added some new observation types, and now you're wondering why they are not working with V5.0? Is that correct?
First, adding the unit group assignments to units.py is never a good idea, because units.py will get replaced in the next upgrade. Instead, you should add them to any user code (that is, code that lives under the subdirectory 'bin/user') because that never gets touched. Most customizations involve some bit of Python code (such as a search list extension, etc.), and that's a good place to put the assignment. Alternatively, if there is no Python code involved, you can put it in user/extensions.py --- that's what it's there for.
Second, I hope you did not literally make the additions to units.py that you showed below. That would cause obs_group_dict to forget all the WeeWX native types! Same with USUnits.
Give it a look. If you're still confused, come back here and we'll see if we can straighten things out.