Thank you for this — it would seem that in the year and a half since I wrote that note, the file on Google Play Music has been fixed and/or re-compressed. So I don’t hear the difference any more either!
When I first heard the issue, I had two other people independently verify it to make sure I wasn’t crazy.
It’s actually not uncommon for issues like this to get fixed over time. Sometimes music companies will deliver better masters to the streaming services, and other times it’s just due to improvements in compression technology that benefit the entire library. The Mastered for iTunes program lead to a lot of higher quality masters getting deployed in general.
I will publish an update to my update so that future readers aren’t mislead by my now-outdated article.