I'm a bit surprised by your claim that the neck bore didn't change. Where does your information come from?Thomann.de's translation are not super accurate.
The neck on the Supreme has a similar bore compared to other Selmer neck, yet the neck profile is similar to a Series III/Axos tenor.
The neck collar is wider, so the Supreme tenor neck does NOT fit on any other Selmer tenor, unless you remove the stock neck collar and replace with another one with a standard diameter (27,45/27,50 mm, before final fitting).
Selmer Supreme Tenor Sax SE-TSULTenor Saxophone in Bb Dark gold lacquer, Strong projection due to enlarged bore at the S-bow, New bore and tone hole scale, Completely optimised ergonomics, Adjustable, concentric 3-point S-bow receiver, Nickel silver S-bow clamping ring, Directly...www.thomann.de
Here is a much more reliable technical summary:
Selmer Supreme Tenor Saxophone - Sax.co.uk
After 8 years of secret development, Selmer Paris reveal to us their ‘best tenor saxophone ever designed’ After 100 years of innovation, design, and manufacturing of the saxophone, Henri SELMER Paris redefines the modern identity of the tenor saxophone with the SUPREME.
and they mention a bore modification for the neck.
So, the new Supreme tenor neck can probably not be retrofitted to an older model --for the alto, they are selling the Supreme neck separately as an improvement.