It should be used as a planning tool. The best use case is comparing pacing scenarios, not assuming a single predicted time is guaranteed.

Transitions are part of the race. Athletes often lose more meaningful time there than they expect.

As a directional heuristic. The tool makes the assumption visible because bike execution does affect the run, but the exact penalty is not personalized physiology.

No. They are starting estimates anchored to common endurance-sport guidance, then adjusted only by broad factors like duration, temperature, and sweat profile.