Diving into the data, there are 21 Philly precincts that aren't reporting anywhere near their full vote, all in heavy D areas of the city... https://results.philadelphiavotes.com/VoterTurnoutDetails.aspx?

Turnout city-wide is currently at 61.4% of registered voters, but all of these 21 divisions reported less than 30% of RV's ballots counted, with a heavy concentration in the 27th Ward around University City.

And, there are plenty of divisions in the 30%-40% range as well.

If this is where the remaining Philadelphia mail vote is from, it's bound to be even more Biden-friendly than the mail vote of the city as a whole, since almost all of the Trump-friendly precincts in NE/South Philly are at high turnout.

If anything, I think people doing simple extrapolation are *underestimating* the additional margin Biden could get from the remaining uncounted Philly ballots, for this reason.

For the time being, Philadelphia is reporting an unusually low turnout increase and an unusually high pro-Trump margin shift vs. '16 than other counties in PA/other states (Wayne, Milwaukee, etc.).

The nature of the outstanding vote could help resolve these divergences.

And yes, dorms are closed at Penn/Drexel. But is it possible many student mail ballots are still uncounted in 27th Ward divisions w/ only 11%-15% turnout reported so far? Also, it doesn't explain the outlier-ish low tallies in the 15 divisions that aren't in the 27th.