The tractate narrates the daily service circumstantially, from the priests rising to the completion of the offering, and that circumstantiality is exactly what makes its status hard to judge: a literary reconstruction written to be persuasive would look the same. It was redacted long after the last offering was made, and no pre-70 source describes the sequence in comparable detail.
What would resolve this A point-by-point comparison of the tractate against Josephus, Philo, the Temple Scroll and the Qumran calendrical material, separating items with independent support from items attested only there, would show how much of the sequence is anchored. Priestly course inscriptions and any further Temple-period administrative material would add anchor points.
OpenRabbinics, Second Temple history, Dead Sea Scrolls studiesShaye J. D. Cohen, From the Maccabees to the Mishnah