The official definition of a homebuilt aircraft is that it takes more than 500 hr to build. In that context these sort of estimates look pretty sad. Yes it takes quite a while to strip and sort things out. But at the end of the day A&C hs nailed it - this is a methid of extracting money from HMG - it has very little to do with real engineering.
My aorrame had has a major strength upgrade - it took us about 30 odd hours - including upgrading the centre section and balancing the ailerons.
It simply cannot take this sort of time for straight forward mods!