I can reproduce the effect though ...Well now I'm confused. Testing this after the report in GMF I couldn't reproduce this. Now I can. I'm not sure what accounts for the change.
I did two things: I changed the group's Def Sub Setting to UTC, and I created two new events. Changing the group's Def Sub Setting to EST hasn't corrected the problem, so it seems not to be the issue. At least not in a direct way.
Possibly the act of creating new events caused something to get lodged (or dislodged) somewhere that causes my Feed page to now be shown in PST regardless of my Account's timezone?
I have the same problem when my account time zone is EST: the group's Upcoming Events list on the Feed page shows them in PST, whereas the Your Calendar page and the group's Calendar page shows them correctly in EST.
Another user account with PST timezone sees them in PST in all three places.