Does terminal temperature rating apply to grounding conductors too?

Yes. Nothing in 110.14(C) carves out an exception for equipment grounding conductors or bonding jumpers. The rule sets the ampacity of conductors at a termination based on the lowest temperature rating of any connected termination, conductor, or device, and it applies to every conductor landed at that point, current carrying or not. A grounding conductor terminated on a 60 degree C rated lug in a panel that only has 60 degree C terminations is evaluated the same way a hot or neutral would be.

Why this confuses people

Grounding conductors do not carry continuous current in normal operation, so it feels like the ampacity table should not matter. But 110.14(C) is about the terminal itself, not about how much current normally flows. The termination rating protects the connection from a fault condition and from heat generated by adjacent conductors in the same lug or bar. Equipment grounding conductor sizing already comes from Table 250.122 based on the rating of the overcurrent device, and that sized conductor still has to physically fit and be rated for the terminal it lands on.

Where it actually bites in the field

The practical trip point is oversized equipment grounding conductors, when someone upsizes an EGC for mechanical protection or to match a large feeder and then discovers the ground bar lugs are only rated for a smaller conductor size or a lower temperature rating. Read the panel label and the lug torque and range specifications before landing an oversized ground, because the terminal limitation applies whether the conductor is hot, neutral, or ground.

Field takeaway

Treat every conductor at a termination the same way under 110.14(C), including grounds and bonding jumpers. Check the equipment label for terminal temperature rating and conductor range before assuming an upsized ground conductor will land cleanly.