I ended up occasionally chugging about half a liter of water before going, because this started happening.
That seems to actually do something very useful when I think I've not had enough water prior, but I don't actually know the details of how the body moves and uses that water. It intuitively feels like 2-3 minutes should be too short of a time-span to start doing useful work, but it still seems to work.
In general not using piddly little 0.2l glasses and instead keeping a large glass or bottle with me isn't just helpful, it's vitally important. I simply can't get by occasionally drinking small glasses of water. Other than the first day I'd resolve to start drinking more water again, I never went to fill them up enough times to actually get sufficient hydration for my size.
Additionally, I've learnt to feel my hydration on my lips, if they're dry I need a drink. But I am an unreliable, irrational actor. I don't always pay enough attention, or stay on top of things even if I notice, so I'm likely to resort to desperately chugging water again.
Chiming behind the lemming who said the water a few minutes prior going won't do anything. It certainly won't do absolutely anything no matter how much you drink. Once the bowel absorbs the water, adding more water to your body won't restore moisture to the stool.
What probably happened in your case is simply peristaltic movement, some people are more sensitive to it. So chugging a generous amount of water stimulates your gut tissues and encourages things to get moving along.
Going back to the water - of course if you stay hydrated and keep things hydrated it will help. But you cannot rehydrate a stool just by drinking.
The way I understand it is that your colon will work harder to reclaim water if you’re dehydrated, so staying hydrated will help keep stool softer overall. That said, rehydrating while constipated (or immediately before a bowel movement) won’t make a real difference since the water has already been absorbed from the stool and it can’t add it back.
I would imagine your drinking lots of water before, if you do it consistently, is probably just contributing to your overall hydration which makes it easier next time.
Me too, once held too long when i was busy and kept hitting the 'snooze button' on going all day long, end of the day i dropped something that resembled a hand grenade, with the little square-ish ridges and everything. The pain, the relief, the lasting butthole tenderness afterwards.