I think its important for a beginner to have a setup horn, mouthpiece and reed that doesn't hold them back because fighting with a poor unregulated setup only adds to the difficulty.
That said there are downsides for a beginner to having a top pro sax too early.
1, How is a beginner going to pick from the many choices that there is available, they will still more or less sound the same as they did on the beginner sax as they won't be able to understand what makes the pro horn better.
2, Many beginners give up playing in the first couple of years so then may have lost a considerable amount of money when they sell because its not for them.
3, If the player continues to play and then realises this pro horn in 5 years is not for them because they favour another brand or maybe wants to go down the vintage route they again lose a lot of money on the horn and have to pay lots more on the horn that they want now they have more experience in choosing what's right.
There are ways round the downsides like buying secondhand although that's a minefield in itself and of course money might not be a problem for some.