New CV axles come with a flange that is not on the old ones. Also replacing the front wheel bearings
The flange doesn't contact anything but I want to be sure it was okay to leave it on or not.
Most aftermarket manufacturers try to "universalize" their parts as much as possible, using interchangeable subassemblies which may not be identical to the OE part on a particular model, but still fit and do the job. That's probably what you have there. So long as there's no interference, I doubt it will cause problems.
Once I removed the driver side CV axle I found it did have the same flange, only rusty. Been driving with that one on for at least 3 years so should be fine.