Thank you for sharing the example, Mike.
I have replicated the same behavior in the vanilla version https://jsfiddle.net/wjmug84z/
I have reported the issue on our Github board https://github.com/handsontable/handsontable/issues/5772
The documentation says that it can only be a number, but it should be confirmed by a developer.
I will let you know as soon as we get some updates.