I would think that not all roofers are that stupid and that if it is removed at the base and re-attached plum it would be in the ballpark until dish can come peak it.
My friends land lord had the roofers remove the directv dish when they put a new roof on so I reattached to the deck keeping the the base the same direction as it was on the roof and what do you know it had a great signal no need to call for a repoint. And as you know a slimline can be more tricky then a 1000 dish.
I know some of you installers think your work takes the same skill level as a brain surgeon, but............lol
Nobody ever claimed that we're brain surgeons, in fact we get paid more like the orderly who cleans up afterward.
But just like most anything else if it's done right with the right tools by somebody who has a lot of experience then obviously it's going to be done better than by and inexperienced amateur without the proper tools. We use the right lags, roof sealing and oh yea, that $800 meter. Maybe you got lucky with your Slimline installation but I assure you that was not what normally happens.