Indeed, this happens often when what is built is less than the artist concept advertised.No budget cut.
According to insiders, Disney does not want to allocate more budget than what was already planned in the expansion plan, and the initial vision for the ride did not fit within this budget (~€ 40 Million in excess). Ultimately, DLP was able to secure a bit more money, but Disney will not give more. A budget cut is when a project is about to be funded, and at the last minute, Disney revises the proposed budget downwards compared to what had been promised.
The final version of the ride has been greenlit last week, they can now move foward.
As you've said, it's not the budget being cut. The problem is that it's over-budget in spending. And so, to stay within the budget, the *scope* of the attraction is cut back.
Disney isn't taking money away. It's bad at estimating the final cost, or, just is bad at staying within budget. That's why elements get cut (for the most part). Disney is spending the money it allocated, only, that money is buying less than what they thought it would.