The hours that folk have problems with is when 2 folk fly a single crew aircraft and both of them log the hours.
and that happens when the pilot in the left seat is flying under the hood and the guy in the right seat is therefore acting as Safety Pilot. Under those circumstances under FAA regulations both may log PIC time which is not recognized by other authorities.
In that case I don't understand why it's so popular to go to the US to do hour building?
because it is generally perceived as being a cheaper option.
However, the better argument is that you can usually accumulate more hours due to the better weather in a shorter time period.
There is no point sharing time building with another pilot if you are time constrained as you only end up logging half the time - which is not the purpose - unless of course you are happy to double the time spent on the trip.