I know that’s what many pros do, with intentional disregard to the IRS 1041 instructions:

“Final Return
Check this box if this is a final return
because the estate or trust has
terminated. Also, check the ‘Final K-1'
box at the top of Schedule K-1.”

But do you have some source for the practice? And I don’t believe it is mandatory in a case like this, where the fiduciary does not want K-1s to be issued. If the income was capital gains, it’s quite possible that they would not flow through without the “final” designation.

For a probate estate, the question is often when the court case can be closed even if a residual amount is held for contingent claims. That’s determined under local rules and practice.