It looks like several of the pins have pull-ups on them on the board.

If you look at the schematic, you'll see in the UEXT section:

That there are pull-ups on GPIO16, GPI36, GPIO13 and GPIO5. So this explains the results you see on GPI36 and GPIO13.

GPIO0 also has a pull-up (in the ESP-WROOM-32 MODULE section). GPIO15 and GPIO0 have one each in the SD/MMC Card section.

There are quite a few more pull-ups here and there. Looks like there aren't many pins floating on the board. Also see the Notes section at the bottom of the schematic for additional pull-up/down info related to bootstrapping.

It looks like several of the pins have pull-ups on them on the board.

If you look at the schematic, you'll see in the UEXT section:

That there are pull-ups on GPIO16, GPI36, GPIO13 and GPIO5. So this explains the results you see on GPI36 and GPIO13.

GPIO0 also has a pull-up (in the ESP-WROOM-32 MODULE section). GPIO15 and GPIO2 have one each in the SD/MMC Card section.

There are quite a few more pull-ups here and there. Looks like there aren't many pins floating on the board. Also see the Notes section at the bottom of the schematic for additional pull-up/down info related to bootstrapping.