I'd prefer that the dimensions be accurate in the design... things like tolerances in manufacturing, etc... here's an edit that shows where the B arc should be in comparison to where he has the slot walls.
Also TE and other companies always have the disclaimer concerning their downloadable models - and I've had many a go-around with Snap and esp. Ultralibrarian about them not being correct. I even had one email back from Snap that stated they don't always go by the Mfg rec's... They eventually retracted that statement.
So, yea - I think in this day and age stuff should be as nutz-dead-on as it can be in the design files (well, as on as Altium will allow with their rounding errors). There's enough silly that happens in fab.