You can still buy full-measure 2x4 lumber outside the United States.
In Iceland, the lumber yards sell Canadian lumber, rough and full
measure (in inches) but described metric by the locals. My brother
went to a lumber yard in Sweden and asked for a piece of lumber in
metric, and the clerk said, "Oh, you mean a two by four."  Here in
Delaware the local sawmills will gladly provide full-measure lumber.

In the old days, oak framing was put up green, so that it would
shrink and lock. Then the carpenters "levelled" the floors with an
adz. As a result we often find very thin joists in old floors because
they took a big twist.

In the days before kiln-dried lumber, a carpenter was expected to
know enough about grain to avoid unpleasant shrinking and twisting
events.