Why does mySQL automatically add display length to numeric values when adding zerofill property
In the past, INT(5) was identical to INT.  The number was useful only when ZEROFILL was also specified.
In the future, ZEROFILL and the number will go away.  This incompatible change is predicted for some time in 8.0.xx.  You are probably seeing some step toward it.
Zerofill is extremely rarely used.  US Zipcodes stored in MEDIUMINT(5) UNSIGNED ZEROFILL is the only case I can think of off-hand.
When Zerofill goes away, there are workarounds for the rare cases where you really need it.
The number confuses a lot of people.  It takes time for newbies to understand that it is normally of no use.
Although DESCRIBE and information_schema.TABLES are tempting for displaying the schema for a table, please get in the habit of using SHOW CREATE TABLE; it rolls the useful information together in a canonical form.