Splitting a treble staff does not create a true bass staff

Expected behavior:

Splitting a treble staff creates a bass staff containing the split notes.

Actual behavior:

Splitting a treble staff creates another treble staff that's disguised as a bass staff by having a bass clef applied to it.

Steps to reproduce:

1. Create a new score with just a treble staff.
2. Right-click the staff and choose Split Staff… from the popup menu.
3. In the Split Staff dialog, choose any split point and click OK.
4. Observe that there is now what appears to be a bass staff below the treble staff.
5. Go to Edit | Instruments….
6. In the Instruments dialog, observe that there are two treble staves, not one treble and one bass.
7. Cancel out of the Instruments dialog.
8. Select the bass clef and press the Delete key.
9. Observe that the bass clef is deleted, unmasking the deceitful treble clef and revealing the true insidious high-pitched nature of the staff.

Workaround:

1. After splitting the staff, cut or copy the entire contents of the “bass” staff into the clipboard.
2. Go to Edit | Instruments…, then delete the fake bass staff and create a real one.
3. Paste the contents of the clipboard into the real bass staff.

Version information:

OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.4.2.9788, revision: 148e43f