This is very similiar to what’s discussed in Download or view esp8266 file system for ESP8266/ESP32.
Basically, if you want to extract the LittleFS filesystem content from the Pico without there being functionality programmed in your sketch to print it out, you can use the technique of downloading the flash content (or just the part where the filesystem would be, the address is visible in the build log) into a binary file using download tools like picotool or openocd and then run the mklittlefs tool in unpack mode (--unpack) with the right parameters (such as the block and page size used in the initial LittleFS configuration).
So yeah that path is not yet implemented in an automated, “one button click” way. But I see why that would be usefull and I’ll look into adding it. What it’ll come down to in the end is just running something like
picotool save --range 0x101ff000 0x1027f000 littlefs.bin
mklittlefs -b 4096 -p 256 --unpack "extracted_files" "littlefs.bin"
(addresses depending on the flash size and chosen filesystem size per platformio.ini of course)
Of course, this doesn’t stop you from programming a readout functionality into your firmware. Your firmware could e.g. react to a special serial command and it’ll do the whole LittleFS.open(), .read(), etc., like shown in the official examples