Cut Wire at Furnace

[George]

Please help me figure out if this a problem or not. The furnace works but I have found a cut wire from the thermostat.
At the furnace there is a pair of wires from the thermostat. Both of these RED and WHITE wires are crimped to the furnace BLUE wire. The WHITE wire has been cut, see attached photo.
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The t’stat wiring diagram labels the RED as +12VDC and the WHITE as FURNACE.
The furnace wiring diagram labels the BLUE wire as THERMOSTAT.
The furnace BLUE/WHITE wire is not connected to anything. Labeled POWER TO THERMOSTAT.
Should this WHITE wire be repaired?
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I might mention that all 3 butt splices were tucked into the squirrel cage and the -12VDC splice was worn through. The white wire may have been cut by the squirrel cage but it seems unlikely.
If you're wondering why I have the cover off – I'm painting it. Suburban's idea of weatherproof paint leaves something to be desired. Chalked up after <2 years.
I've also sent this to Alliance Service and will post any response from them as I receive it.

 

[George]

Update: Alliance contacted me and advised repairing the white wire. I did so and the furnace fires and shuts down as expected.
I replied that I am still confused as to why the RED *and* WHITE wires are both terminated to the furnace BLUE wire. I also asked where typically this 2-conductor cable is spliced into the 6-conductor from the thermostat – at the rooftop A/C?

 

[George]

Update to Update: 🙃
Alliance Service confirms that the 2-conductor cable picks up the white wire from the thermostat at the rooftop A/C unit.
I haven't climbed up there but I suppose they just used both the RED and WHITE for redundancy. This actually saved me from an inoperative furnace since the white wire was cut.
May I add that replies from Alliance were timely and appreciated.