The Congressional Research Service his issued a revised “Coast Guard Polar Security Cutter (Polar Icebreaker) Program: Background and Issues for Congress” updated 9 August 2019.
It includes a short appendix (Appendix E, pp 63-66) on the issue of a potential new Great Lakes icebreaker. The final paragraph of that appendix states:
“An examination of procurement costs for Mackinaw, the National Science Foundation’s ice-capable research ship Sikuliaq, new oceanographic research ships being procured for NOAA, and OPCs suggests that a new Mackinaw-sized heavy Great Lakes icebreaker built in a U.S. shipyard might have a design and construction cost between $175 million and $300 million, depending on its exact capabilities and the acquisition strategy employed. The design portion of the ship’s cost might be reduced if Mackinaw’s design or the design of some other existing icebreaker were to be used as the parent design. Depending on the capabilities and other work load of the shipyard selected to build the ship, the construction time for a new heavy Great Lakes icebreaker might be less than that of a new heavy polar icebreaker.”
Chuck Hill's CG Blog 
A new revision was published on 4 October; the link in your post points to the latest version.
Do you recall seeing the chapter “Parent Design and PSC Design” on page 15 before? At least the 19 September 2019 revision from everycrsreport.com didn’t have it. Looks like someone is having doubts about the parent design which has been dubbed as being “in design and construction” (as of today the Germans have not even selected the shipyard yet, let alone begun construction).
Makes me wonder if they somehow managed to confuse the new design with the 40 year old icebreaker of the same name.
It’s more likely that someone has made the Polarstern II design appear to be more mature than it actually is.