Nano RP2040: reported size of flash is wrong in boot mode

If the nano RP2040 is connected in boot-mode, thus exporting a file system named RPI-RP2, the host pc, a Linux Mint 20.1 laptop, reports a file system size of 128 [MiB]. As circuitPython is installed on this nano, it normally presents a file system named CIRCUITPY. The reported size of this file system is correct, 15 [MiB].

In boot mode:
user@ticiv ~ $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
....
sdb 8:16 1 128M 0 disk
└─sdb1 8:17 1 128M 0 part /media/user/RPI-RP2

In normal mode:
user@ticiv ~ $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
....
sdb 8:16 1 15M 0 disk
└─sdb1 8:17 1 15M 0 part /media/user/CIRCUITPY

As I know that the nano has a flash of 16 [MiB], this is not a big problem. However, it could cause one to copy an image which exceeds the physical size of the flash without the pc giving any warning/error in advance.

Per One chip to flash them all, the discrepancy seems to be intentional. Note that as the file system is completely virtualized, its indicated size has little relevance. As far as I remeber, the UF2 format is also close to 50 % overhead, assuming 256-byte flash pages.