Bromide is the only difference.. From what I remember from Mr Jolly's note the bromide(restrainer) changes the grain structure or clumping structure during the second development, which then gives a different type of tone for the second development. I have seen the difference just can't explain it well.
Quote Originally Posted by Photo Engineer View Post

You get one tone from the first developer and another tone from the positive image in the second developer. If bromide is the only difference, then it is due to bromide, but if there are changes in Metol and / or HQ, then all bets are off. Same for Sulfite. Even BTAZ or PMT can alter the image tone as is well known.

You probably cannot reverse the order of the tones though unless you add a wash step before the second developer such that all of "toning" chemistry A is removed before developer B is entered and the flash is done.