Thing is these sort of issues happen from time to time its how the railway responds to them that matters and Do Not Travel cannot be the deafult answer. The main line could be terminated short at C.Jcn or Wimbledon but they don't in fact not even running upto Woking by the looks of it at 0900. They have Windsor side then divert into there and thin the Windsor side services to free up some platforms but they don't. GBR needs to get a grip of this if its to stand for anything.
Being an ex-SWR control bod, I can tell you that that is utterly unworkable without already thinning out the service
and dealing with the masses of crew who would need to be shuttled back and forth. Trains are every 2-3 minutes in the up direction in the morning - but can take upwards of 5 minutes to empty out at places like Clapham and Wimbledon, which aren't even long enough to accomodate the largest trains. You then also need to account for crossing back over to the down lines on the reverse (which you're unlikely to be able to do if your train is already longer than the platform), so the train needs to move on toward Waterloo or go into a depot which the driver may not sign.
And that's before looking at what we're actually going to do with 1000 people you've just turfed off at these stations who wanted to be in Central London, not zone 3, and the impact it has on the networks around it.
All of this needs to be managed by a single TSM and mostly by phone call to signallers, stations, and guards. On average I saw a TSM make and implement around 1 decision every 3-4 minutes
at quickest, and usually closer to 5 minutes by the time they'd managed to get hold of the guard who didn't have their phone on or lost their signal. They're also dealing with call-ins because crew want to know what's going on, or want to confirm their service actually is terminating because they've seen it on Tyrell but don't trust it.
Now, I'm not saying there aren't better solutions - of course there are. Rapid timetable replanning, AI-supported problem solving, automated diagram notifications for service changes, ATSMs to support logging and tracking, more crew and increased route knowledge, full-crew working and simpler diagramming - but these all cost money because they reduce efficiency, and money is the one thing the railway isn't getting much of at the moment. Every year it's "net subsidy reduction", which typically means marketing works because it has a positive ROI, but things that don't have an ROI that can be realised within 12 months are not likely to happen.
Apologies if this comes off as a bit of a rant - I promise it's not, but more of a look at railway realities at a strategic level. The complaint is a valid one, and yes, there should be more opportunities to curtail services at sensible locations, but ultimately, this is a decision taken at political levels, when there are other, more pressing requirements for government money.