On the kids Lenovo Chromebook copy that I have to answer any questions they come up with, "no" I have not used those subsystems. Those units are ARM processor units. And the 2nd gen of these are not very powerful and lag the Intel based Chromebook I have. The kids use them in tablet mode versus desktopl/aptop by unsnapping the keyboards. They make video calls, take photos, play games, etc using the tablets more/less like a cell phone over WiFi. They, also, have a separate Chromebook issued by the school systems.
On the Acer, I haven't used those subsystem in months as I have been using PCs for my Linux work, of late. Will have to revisit those subsystems.
I did use the 'public' ChromeOS distros on a couple test machines several months ago for mere discovery.
I know that ChromeOS is going to undergo a 'massive" change during Google's "Summer of Code" soon as it starts to prepare for the upcoming school years. And I am expecting that will impact my units as a result.
I stay up to date on these units to mimic what my grandkids see, so as to support them with questions. They, like other seniors I have guided to Chromebooks since 2015, have never come back with complaints or questions ever. Its a pattern that suggest a behavior never seen in the DOS/Windows/OS2 eras of the past with these non-technical users. So, it appears, for this group, if its intuitive, stable, and easy to navigate I wont get follow-up questions. (YES, I know this paragraph is off-track)
I just took a quick look thru the developers forum and am not seeing bug reports or questions on the RAM impacts you are seeing. Even though I think you are correct, I wonder the culprit that is causing the significant change you have uncovered.