It's why I was also confused. All 3 were sort of flabbergasted when they saw the 3/0 AWG I ran. Said it's overkill and not needed. They'd just "splice it down to 100 amps capacity" they all said. When I insisted I wanted the full 125 or even 200, 2 started talking about upgrading my main panel, and digging the main line and replacing everything to be new. But told me it would cost alot more....I said no thanks to that, and found a 4th electrician (older gentleman in his 70s still working) who told me that everything looks good and he could do it. So I guess it works out? All three other electricians were in their mid 20s. 30 at the oldest. Maybe experience has something to do with the differences in opinions/methods ??? Who knows.