Cannot send OS from the boot screen

[adriweb]

This fails:

[CEmu] Transferring OS: basecode 5.8
[dusb_transition] loop. state = DUSB_OS_PING_WAIT_STATE
[USB] R 00 00 00 04 02 00 00 03 FF
[dusb_transition] original_state = DUSB_OS_PING_WAIT_STATE
[dusb_transition] loop. state = DUSB_OS_PING_STATE
[dusb_transition] original_state = DUSB_OS_PING_STATE
[dusb_transition] loop. state = DUSB_OS_PING_ACK_WAIT_STATE
[USB] S 00 00 00 10 04 00 00 00 0A 00 01 00 03 00 01 00 00 00 00 07 D0
[dusb_transition] original_state = DUSB_OS_PING_ACK_WAIT_STATE
[dusb_transition] loop. state = DUSB_OS_PING_ACK_STATE
[dusb_transition] original_state = DUSB_OS_PING_ACK_STATE
[dusb_transition] loop. state = DUSB_OS_MODE_SET_WAIT_STATE
[USB] R 00 00 00 02 05 E0 00

whereas this is OK:

[CEmu] Transferring OS: basecode 5.8
[dusb_transition] loop. state = DUSB_SET_CONFIG_STATE
[USB] R 00 00 00 04 02 00 00 03 FF
[dusb_transition] original_state = DUSB_SET_CONFIG_STATE
[dusb_transition] loop. state = DUSB_BUF_SIZE_REQ_WAIT_STATE
[USB] S 00 00 00 10 04 00 00 00 0A 00 01 00 02 00 01 00 00 00 00 0F A0
[dusb_transition] original_state = DUSB_BUF_SIZE_REQ_WAIT_STATE
[dusb_transition] loop. state = DUSB_BUF_SIZE_REQ_STATE
[USB] R 00 00 00 02 05 E0 00

i.e. what differs is:
S 00 00 00 10 04 00 00 00 0A 00 01 00 03 00 01 00 00 00 00 07 D0 vs
S 00 00 00 10 04 00 00 00 0A 00 01 00 02 00 01 00 00 00 00 0F A0

Looks like basic vs normal mode, and boot doesn't handle normal mode.
So why is normal mode there?