Import only 1 custom block content, how to?

Problem/Motivation

Hi,

I am not sure what Full cutom block import actually does,

Full
Function to fully import the custom blocks.
Basically a safe import with update actions for already existing custom blocks.

Deletes any custom blocks not in config.
Imports all custom blocks in config.

So the goal is to update 1 existing block content from dev to production.
And the docs says "Deletes any custom blocks not in config."
I have done on DEV:
1. exported all custom blocks
2. Drush cex -y
On production
1. Drush cim
But now I want to still import only 1 custom block (by selecting that from the checkbox list)

Will this import only the selected block and its content using "import custom blocks (full)"

The phrase "Deletes any custom blocks not in config." just is confusing. Yes all blocks
are in the config but I want to import only 1 block.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes