T-3/5/10 is one thing, and the good figures there show that it's a relatively punctual TOC. Similarly, the low cancellation statistics show that it's an operator that fairly reliably delivers the timetable it promises.That's not entirely fair. In terms of punctuality of trains actually run, Chiltern's Moving Annual Average as at the end of Period 9 (10th December 2022) put them 8th out of 24 operators (which includes the Open Access Operators, concessions such as London Overground and Merseyrail, Caledonian Sleeper, ScotRail, and TfW Rail) when it comes to T-3 (no more than 3 minutes late at every scheduled station stop), T-5 (no more than 5 minutes late) and T-10 (no more than 10 minutes late).
If you just count the former DfT franchised operators, they come third on all three counts (behind c2c and Greater Anglia.) Least punctual on all three counts is Avanti, with a T-3 MAA of just 64% (compared to 93.9% for Merseyrail, the top performer on all three counts.)
In terms of cancellations, again measured against the advertised timetable, Chiltern's MAA at the end of Period 9 puts them 2nd (at 1.84%) behind c2c (at 1.77%), with Avanti right at the bottom on 8.36%.
That said, I would agree that the service provision since Covid hit has been rubbish, with extended journey times and reduced frequencies and train lengths, doubly so during this most recent bout of industrial action. It remains to be seen what happens when what passes for normality returns next month, and at the May timetable change.
But none of that is a measurement of how useful the timetable is. It doesn't in any way reflect the fact that major towns such as Warwick are being essentially cut off from the rail network for three weeks. Other places are also badly affected.
Unfortunately, reliability and punctuality is useless if there's no service to speak of.