Far from nonsense. Two very real financial impacts happening here.
Cash Flow management is first. Cash is King. While the P&L impact is depreciated as you point out, the cash flow is short term...gotta pay for the materials and contractors. Delaying the build delays the impact to the cash flow statement. In a COVID situation where inbound cash is pinched, controlling the outflows matters. In fact, in terms of capital planning, targets are set for the divisions in context of yearly capital outlays...not the subsequent depreciation hit to the P&L.
Secondly, pushing out opening also pushes out the P&L impact of said depreciation along with all other associated pre-opening costs that have been parked in pre-paids awaiting the opening date. If the park is at 30% capacity today, you certainly don't want year one of Tron (and Guardians and Rat and...) depreciation weighing down your P&L.
Since you brought up Velocicoaster, by your theory Universal should be chugging away on Epic Universe construction since it's depreciated. Keep building it! You won't see it hit until 2025! Nope, that's not how cash works. And it's why that construction site is a ghost town.
So incompetence it is not. It's corporate financial management and it's what you need to do when you are managing a company with a $300B+ market cap. We may not always like the in-park impact (and it may not need to go as deep) but it's reality.