I'd say it is common for people to say things when the ball is on its way to the opponent, but it is not common for them to yell these things.
People frequently flub a shot and chastise themselves before the point is over. No one cares.
People sometimes correct their positioning as their opponents are preparing to hit: "Stay where you are," "Watch the line." Usually people don't scream these things. Again, no one cares.
Are you saying folks don't do that where you are?
Correcting positioning is common. I do that myself but it's usually right after I hit the ball and I notice my partner is likely to move somewhere that doesnt work.
But that normally only happens in ambiguous situations or when I have a partner that doesn't know how to cover the court properly, we dont have to do it on every single point. Id say I might end up doing that 2-3 times a match if I have a good partner (or someone who just works well with me).
It probably violates the rule, but I think it's understood that at some point you dont want to interfere with your opponent's shot. (so either do it quietly or soon enough that it doesnt affect them)
It's usually just a select few though that moan right after they think they flubbed a shot.
It kind of depends though. If someone just does it out of the blue and it screws up your point there isnt much you can do about it. (after all once you try for the ball it's not hindrance anymore)
But if someone has a habit of doing it a lot then it becomes a bigger problem. I have a friend like that, who if he gives you an easy put away he cant help himself so he will moan about it.
He does the same thing when he thinks that he's hit it out only to have it fall in. He even knows it's hindrance though and since he cant control himself he'll usually let us take the point.
It's kind of like people who catch the ball in midair around here, there are usually habitual offenders and we all know who they are because it sticks out.
Hindrance is really rarely called though because you would have to call it BEFORE you hit the ball. In most cases nobody will think to do that especially if it just happens out of the blue.
So it's not really just a rule thing, it's more like a courtesy thing.
You should respect your opponents and be aware of trying not to disturb them when they are going after or hitting their shots. Saying that "everyone talks and makes noise so it's okay" doesn't make it right.
As far as proclaiming that your opponent is "going to get the ball", that's crazy.
About the only time I could see doing that is if you smack the ball sideways onto an adjacent court where everyone thinks it's been put away, but one of your opponents speeds over there somehow and hits the ball from the center line on that court onto yours which is a pretty unreal thing to do.
It happened to me once and I wished I would of said something to my partner who was just standing around thinking the point was over.