UI Builder Background Size doesn't stay in percent when values are dragged

Steps to reproduce:

1. Create and open a new project
2. Create and open a new UI Document file
3. Add and select a Visual Element in the UI Document
4. Expand the Background section in the UI Builder's Inspector
5. Set the Width type to '%'
6. Drag the value and observe the field

Actual results: The Width type changes to 'px'

Expected results: The Width type stays at '%'

Reproducible with versions: 6000.5.0a5, 6000.5.0b5, 6000.6.0a3

Not reproducible with versions: 6000.0.73f1, 6000.3.13f1, 6000.4.3f1, 6000.5.0a4,

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• Does not affect any other field
• The Height field is also affected