Cancelling split with heightmap resolution < 33 deletes original tile being split

Steps
1. use TerrainToolbox > Create New Terrain to create a terrain with
width=1100
length=1100
height=111
with 4 tiles in X Axis and 4 tiles in Z Axis
and using Import HeightMap = Global with the Canyon03 texture2D from the Terrain Sample Pack
with Tile Height Resolution = 129

2. select one of the tiles from the newly created terrain
3. switch to Terrain Toolbox > Terrain Utilities
4. under the Split section -
5. uncheck box to keep original terrain
6. set to 4 tiles in X Axis and 4 tiles in Z Axis
7. click split button
8. continue past warning: "About to split selected terrain(s), and this process is not undoable!..."
9. at the next warning: "The heightmap resolution of the newly split tiles is 9...", press the *Cancel* button

results: the original tile you were trying to split is deleted. It's no longer in the scene or the heirarchy window
expected results: when you press Cancel in step 9, the operation is aborted and original tile you were trying to split is still present

Does not repro with more generic settings such as:
width=500
length=500
height=111
with 1 tiles in X Axis and 1 tiles in Z Axis
no imported heightmap
with Tile Height Resolution = 129

Issue found using macOS and Unity Editor:
Version: 2020.2.0b7.3288
Revision: 2020.2/staging 1b1252580c64
Built: Tue, 06 Oct 2020 02:13:03 GMT