[bug] why a tree whose check-strictly is false cannot check the node whose children's checkboxes are all disabled?

Element UI version
2.15.14

OS/Browsers version
WIN 10 / chrome 129

Vue version
2.6.14

Reproduction Link
https://codepen.io/josecanul94/pen/RwXbRwO

Steps to reproduce
- create a el-tree with prop check-strictly is false
- a node in the tree whose children all cannot be checked (check Level two 2-1 in example)

What is Expected?
the node in a 'check-strictly' tree is false whose children are all disabled can be checked