We would like to use the "check history" in preconditions tab but we saw the note "This action cannot be used in the statistics of previous Automation Engine versions".The text you are referring is in this section of the documentation :
What does it mean exactly? If we upgrade the engine, will it continue to work with the statistics generated under the older version? Even if we are moving to v12?
This is probably referring to versions older than version 8.
There has been no significant changes in the structure of the statistics (AH) table since then, so this should not be a concern.
Moving up to version 12 should not affect this functionality by any means.