It is the first I've heard of it too but according to this draft spec QR codes can't support binary:

https://datatracker.ietf.org/doc/draft-faltstrom-base45/

"Even in Byte mode a typical QR-code reader tries to interpret a byte sequence as an UTF-8 or ISO/IEC 8859-1 encoded text. Thus QR-codes cannot be used to encode arbitrary binary data directly. Such data has to be converted into an appropriate text before that text could be encoded as a QR-code. Compared to already established Base64, Base32 and Base16 encoding schemes, that are described in RFC 4648 [RFC4648], the Base45 scheme described in this document offer a more compact QR-code encoding."

Here is the output alphabet:

   Value Encoding  Value Encoding  Value Encoding  Value Encoding
      00 0            12 C            24 O            36 Space
      01 1            13 D            25 P            37 $
      02 2            14 E            26 Q            38 %
      03 3            15 F            27 R            39 *
      04 4            16 G            28 S            40 +
      05 5            17 H            29 T            41 -
      06 6            18 I            30 U            42 .
      07 7            19 J            31 V            43 /
      08 8            20 K            32 W            44 :
      09 9            21 L            33 X
      10 A            22 M            34 Y
      11 B            23 N            35 Z

My initial thought is using "Space" as a valid encoded value seems like an enormous foot gun.