Something I learned in the meantime:

While my (virtual) punch cards use some steganography in order to preserve case for modern languages (in fact a hidden row 13 or Z as an additional zone punch), there are more traditional ways to encode lower-case characters on punch cards.

Carl (yes, the Carl seen in CuriousMarc/Marc Verdiell YouTube videos) brought the following enlightenment:

There is indeed Hollerith code (and EBCDIC) for lower case letters - although no keypunch keys to encode them and no print matrix to list them.

lower case letters are x’81’-x’89’, x’91’-x’99’, and x’a2’-x’a9’

For Hollerith code, the letters a-i are 12-0-x where x is 1 to 9, letters j-r are 12-11-x where x is 1 to 9, and letters s-z are 11-0-x where x is 2 to 9.

So, the first ones are EBCDIC, which isn’t applicable in our case (as we’re using plain EBCD), but the Hollerith codes were new to me.

P.S.: In order to see how a zone punch of 12-0, 12-11, or 11-0 fits into the encoding scheme, see the diagram at the bottom of the page in question.