It mostly appeared in games sold in the United Kingdom, as, by the time it was written, the Commodore market in the United States had mostly switched to floppy disk media.
https://en.wikipedia.org/wiki/Invade-a-Load
Loading games on the C64 was a nightmare.... At least with the 3 cassette loaders I owned. The first 1 broke, the second one was returned due to not loading some games and with the 3rd I experimented with adjusting the tape head alignment. Most games would load, but sometimes they would randomly fail. When loading took a up 30 mins (max capacity, most games much less), it would become infuriating! Much finger crossing was done during loading.
This was the tape loader...
https://en.wikipedia.org/wiki/Commodore_64_peripherals#Tape_...