I would like to know what would happen on this hypothetical scenario:
(757/67 but I guess is the same for other a/c)
Eng(n) is running at idle or with power. Eng(n) starter switch rotated to GND.
ECU make switch cuts immediately to AUTO, Eng(n) bleed valves are not commanded to close, start valve NEVER opens and APU bleed valve is kept in the current position.
Start valve opens, Eng(n) bleed valves are commanded closed, APU bleed valve, if APU on, is commanded open. As Eng N2/N3 RPM are greater than 50 %, Start switch cuts to AUTO, Start valve closes, Eng and APU bleed valves perform the same as in a normal start.
A mix of Case 1 and Case 2...