Anaysis #25533

Analysis

It seems, https://github.com/odoo/odoo/pull/10557 got close into this direction.
Provides context: https://github.com/odoo/odoo/pull/15336
Reports the "no-self-triggering" limitation: https://github.com/odoo/odoo/issues/2693

@ged-odoo Some time ago: https://github.com/OCA/web/issues/562#issuecomment-282384372

~Ideally the backend and frontend could communicate a command "`KEEP` (`7`)" for those sub values near...~

https://github.com/odoo/odoo/blob/ef0907d5b0858efbf7702c78698d21fadf0149e7/addons/web/static/src/js/views/basic/basic_model.js#L96-L134


Why not use command 0 through 4 to message a more detailed picture to the client?
https://github.com/odoo/odoo/blob/ef0907d5b0858efbf7702c78698d21fadf0149e7/odoo/fields.py#L2112-L2134
 ... after all the backend can infer this entropy first-hand. And let the client keep un-instructed values untouched.

Seems that someone elase already had a problem with this behavior already:
https://github.com/odoo/odoo/blob/8643175d00fb8ac418af15273cdbce32f9946c50/odoo/addons/base/ir/ir_model.py#L204-L207