We've been to Alaska 3 times and I have never heard of this. Where did you get this info? As far as I know Princess doesn't own any docks - if anything they are owned by Carnival Corp. who in turn own Princess and HAL.
The only port that I know is definitely a tender port for all ships is Sitka.
What ports are you visiting & what ship will you be going on?
Alaska is wonderful and you will have a great time.
i have been to alaska 3 times with HAL and have always docked except in Sitka. HAL is a cruise line with Princess being "grandfathered" in I believe to docking spaces as well as getting permits to Glacier Bay.