127.0.0.1/8 refers to only a single IPv4 address "127.0.0.1" that have the subnet mask 255.255.255.0, but doesn't to 127.0.0.2.
127.0.0.0/8, which is the exact definition of the loopback addresses [1][2], includes what the regex says (127.0.0.0-127.255.255.255).