Nah, there is no way any astronomer studying orbital mechanics in our solar system is rounding pi to 1. There is virtually no practical calculation you could do on the mechanics of the sun or planets where rounding a known constant by a factor of 3 would yield any useful result whatsoever.
Rounding pi to 1 only makes sense when the uncertainty in the numbers is large, not the magnitude of the numbers, and we know the masses and distances of the objects in our solar system to an amazing level of precision!
Plus, the fact that Jupiter is massive enough to actually exert an influence that large on the sun is pretty fucking cool!
Sure, I totally agree that when you’re dealing many with orders of magnitude, the factor of 3 is dwarved by the other uncertainties.
But we’re talking about our solar system, and specifically the orbital mechanics of our planets and sun, where the quantities and scales only span a couple orders of magnitude in total. A factor of 3 absolutely makes a difference. That’s the difference between the orbit of Mercury and the orbit of Earth.
Then there’s the practical point that, regardless of scale, rounding a known constant by that much makes no sense at all, unless you’re trying to estimate huge numbers in your head. If you’re using even the simplest of calculator, estimating pi as 1 is a deliberate choice to reduce accuracy.