The tkapp.split() method has weird behavior. It splits a string recursively, so the type of items and the depth of nesting depends on spaces in string values. For example:

>>> import tkinter
>>> root = tkinter.Tcl()
>>> root.tk.split('Hi')
'Hi'
>>> root.tk.split('Hello "Good bye"')
('Hello', ('Good', 'bye'))

It may work as you meant in some cases (if items at the same level either all have spaces or all do not have spaces), but return unexpected  result for untested cases. It is more robust to use the tkapp.splitlist() method, which split exactly one level and always returns a tuple of strings. It can be used recursively if you need nested lists.

>>> root.tk.splitlist('Hi')
('Hi',)
>>> root.tk.splitlist('Hello "Good bye"')
('Hello', 'Good bye')
>>> [root.tk.splitlist(x) for x in root.tk.splitlist('Hello "Good bye"')]
[('Hello',), ('Good', 'bye')]

New changeset d05b000c6bcd39dba4f4b2656e45954802649562 by Serhiy Storchaka in branch 'master':
bpo-38371: Tkinter: deprecate the split() method. (GH-16584)
https://github.com/python/cpython/commit/d05b000c6bcd39dba4f4b2656e45954802649562

New changeset f235dd0784b92824565c4a4e72adc70fa3eab68f by Erlend Egeberg Aasland in branch 'main':
bpo-38371: Remove deprecated `tkinter` split() method (GH-28237)
https://github.com/python/cpython/commit/f235dd0784b92824565c4a4e72adc70fa3eab68f

New changeset 085ccb0f177988065dbe9ef4c5cda434560066bc by Zachary Ware in branch 'main':
bpo-38371: Remove remaining use of tk.split from bigmem tcl test (GH-29082)
https://github.com/python/cpython/commit/085ccb0f177988065dbe9ef4c5cda434560066bc