Given this:
I can't see why leeway of minutes should be granted.
As I travel in GWR land, and GWR don't have Delay Repay (despite the noises that have been made about it, but that is a discussion for another thread!), it isn't really something that directly affects me. But for the moment assume it would.
If my train is 14 minutes late into Bristol Temple Meads, but because the train shows arrived as it trundles slowly into the far end of the platform (due to the slow speed limits and change in stopping locations put in force after the recent resignalling) the actual time recorded is 13 mins late. It then has to be coupled or decoupled to another unit the doors don't open until 16 minutes late, why should I be denied money back? I was still delayed by 16 mins, but the only record the ToC will have is that it was 13 mins late (even though it didn't actually stop unit. How is that at all a good situation? I would expect the ToC in that scenario to pay up, but based on the current situation, they are not guaranteed to.
The differences are usually marginal. I can only speak from experience, and all cases I have interrogated so far in the last few years (a lot of trains for that matter in various locations), there is only a very small number out by more than 10 seconds.
Well I guess I'll have to provide specific examples when I can then!
I commute from Oldfield Park to Keynsham, and I know that NRE and RTT show the train as arrived at Oldfield Park before the train does come into the platform, we are probably only talking 30 seconds or so, but it is enough to be noticeable, and as ToCs do reject delay repay if its a minute shorter than the time they allow it for, then it can impact people. And that is at a small station where the platform is small, the dwell time is short and there is no coupling / decoupling of units etc.
I also sometimes travel from my girlfriends near Montpellier to Keynsham, and have noticed there that the reporting is even weirder, with a service showing as arrived at Montpellier even though it hasn't yet in reality left Redland!
And then you have entire sections of lines that don't have any real time reporting at all (e.g. Treherbert to Porth on the Cardiff Valley Lines).
Now, I don't know if there is other timing data that is used for Delay Repay etc in these cases (if there is, why can that data not be made public?), but certainly from what a passenger can access, the data is just not accurate at all.