Watchdog in Arduino Library - or at least support by bootloader

Using Arduino Project Guidance
32

Regarding "
Tested on the Mega2560 board once I replaced the bootloader with this working one:

https://raw.github.com/arduino/Arduino-stk500v2-bootloader/master/goodHexFiles/stk500boot_v2_mega2560.hex
"

I found another bootloader (which seems to be the one installed with the Arduino IDE) under
https://github.com/arduino/Arduino/tree/master/hardware/arduino/
bootloaders/stk500v2/stk500boot_v2_mega2560.hex

It has the same file name as "this working one", but its size is 103kB versus 21kB for the other.
Obviously, these are different bootloaders, and should have a different version, means e.g. stk500boot_v3_mega2560.hex for the working one. Besides of this, what are the differences between the two, other than watchdog support?