"INTOL/M082F350 UN873 SALPU/M082F370 UN873..."
Decoded, this means the flight intended to cross INTOL at Mach 0.82 and FL350, proceed along the UN873 airway and cross SALPU at Mach 0.82 and FL370. In other words, the canned flight plan called for a cruise climb from FL350 to FL370 between INTOL and SALPU and before disappearing.
Do we know if this cruise-climb was performed? If it was, would not the A330 have been even more deeply embedded into its "coffin corner?"
Nope, it means that
after SALPU the flight is requesting a level change to FL370. Any change in level would be issued by ATC (whether a cruise climb or not) and would be dependent on other traffic and whether the pilot actually wanted a level change or not from his current level. The pilot wouldn't change level on his own initiative, unless complying with Loss of Communications procedures. In that case there are criteria for making the level change, and based on the filed FPL, it would not occur until after passing SALPU.