The question involves a house with a detached garage that is about 60' away. The feed from the utility spans a considerable distance, whips in the wind and is near trees. The owner wants a subpanel in the garage for hobby activity.

The utility has suggested relocating the man incoming line and meter from the house to the garage and then feeding the house panel as a subpanel. The suggested configuration is a 200 amp panel in the garage with a 100 amp feed underground feed to the house panel.

The question is does the subfeeder need to be bigger than required for 100 amps? A local electrician has suggested that the subfeeder should be sized for 200 amps into the 100 amp panel.

That really doesn’t make sense to me but I am wondering if there is some requirement here I am not aware of.

The incoming lines are the utilities problem. Why make them yours? You don't pay for the line losses and it's the utilities problem to get you reliable power.

I would tell the utility, if they don't like the connection then they can change it at their expense! Who would want a main panel in an unoccupied building anyhow?

Other than that I would put a 60A sub panel in the garage.

The sub-feeder may have to be oversized for voltage drop. For 60A, #4 is good for 128 feet.

Since it is "suggested" It is Owners option. Shorter Span May make it through worse storms. Money is involved here, and As far as can see, If House is subpanel, Then would need bigger wire$, If Garage is sub, smaller wire$, If I had the funds. Would make
Garage Main and house sub panel, 2" PVC with 2-2/0, 1-1/0 and 1 #4 for ground.
Less Voltage Drop, and when you want to up grade just change a breaker. Make sure Panel is Rated for 200 Amps, can use on 100, will be ready for 200, or 150.