OK, trying it with a more normal adapter (Samsung W16-030N1A, 30W). Still only pulls ~230mA, and the trace is a bit more normal:
6911793-6913972 USB PD: Full text: #1 (2879.913750ms): (r2) SRC[0]: SOURCE CAP - [1] [Fixed] 5V 3A (15W) [unconstrained] - [2] [Fixed] 9V 3A (27W) - [3] [Fixed] 15V 2A (30W)
7717970-7720149 USB PD: Full text: #2 (3215.820833ms): (r2) SRC[0]: SOURCE CAP - [1] [Fixed] 5V 3A (15W) [unconstrained] - [2] [Fixed] 9V 3A (27W) - [3] [Fixed] 15V 2A (30W)
7720512-7721700 USB PD: Full text: #3 (3216.880000ms): (r2) SNK[0]: GOOD CRC
7728937-7730445 USB PD: Full text: #4 (3220.390417ms): (r2) SNK[0]: REQUEST - [1] (PDO #3: Fixed 15V) 2A (operating) / 2A (max) [comm_cap]
7730759-7731966 USB PD: Full text: #5 (3221.149583ms): (r2) SRC[0]: GOOD CRC
7733627-7734834 USB PD: Full text: #6 (3222.344583ms): (r2) SRC[1]: ACCEPT
7735201-7736390 USB PD: Full text: #7 (3223.000417ms): (r2) SNK[1]: GOOD CRC
8192161-8193368 USB PD: Full text: #8 (3413.400417ms): (r2) SRC[2]: PS RDY
8193734-8194923 USB PD: Full text: #9 (3414.055833ms): (r2) SNK[2]: GOOD CRC
8215655-8216844 USB PD: Full text: #10 (3423.189583ms): (r2) SNK[1]: DR SWAP
8217162-8218369 USB PD: Full text: #11 (3423.817500ms): (r2) SRC[1]: GOOD CRC
8219302-8220509 USB PD: Full text: #12 (3424.709167ms): (r2) SRC[3]: REJECT
8220874-8222063 USB PD: Full text: #13 (3425.364167ms): (r2) SNK[3]: GOOD CRC