PPL(H) theory credit towards PPL(A)

[scanavos]

I have PPL(H). I want to take PPL(A). According to Commission Regulation (EU) No 1178/2011 3/11/2011 Appendix I 1.2 I must write exams on:
-Principles of Flight
-Operational Procedures
-Flight Performance and Planning
-Aircraft General Knowledge, Navigation

Question 1): Is there any difference between the navigation of an airplane and the navigation of a helicopter?
Question 2):Why the Navigation is not written in this law as a separate subject but is written as a secondary one added to the AGK?
Question 3): Is it written by accident or it is written reasonably in the law that an applicant for another category must write PoF, OP, FPP, AGK (ok for them) and Navigation exam too?

[Saratogapp]

Answer 1)
Things happen faster in a fixed wing, purely because of airspeed. Because of the faster speed, nav errors (off-track errors) are less in a fixed wing if dead reckoning. Conversely, in a rotary wing, you can pull up and have a think. Apart from those obvious little gems, nav is nav...

Answers 2 & 3)
No idea - these abbreviations mean nothing to me, I'm afraid. We don't use these in Oz.