Command block screen is opened before the update packet is received, causing blank and disabled default value controls to be displayed for a while

The bug

When you right click on a customized command block, you will notice empty text fields and/or "Chain" state of the leftmost button, and also disabled "Done" button.

What I expect:
The controls immediately display its values after opening the command block screen or telling you that it is loading.

What actually happened:
After opening the interface all controls are in the default state (except for the leftmost button, it is in "Chain") and disabled "Done" button. Then after a while all controls display its values.

My suggestion is to make the command block screen open when the client received the update packet of the command block block entity, like a chest. Or, tell the user that the command block's data is being loaded.

How to reproduce

1. Enter a lag-inducing command into a powered repeating command block, e.g:

   /execute if entity @e[distance=100000]

2. Close and reopen the command block GUI
   →  The command input field will briefly appear blank