This is very likely because without the full path your shell is using the `time` builtin function of your shell as opposed to using the binary.
The shell's builtin keyword for `time` is more limited in nature than the full `time` binary. This is true of a number of other common unix commands as well, e.g. `echo`. The manpage for your shell should describe the builtins functions.
The shell's builtin keyword for `time` is more limited in nature than the full `time` binary. This is true of a number of other common unix commands as well, e.g. `echo`. The manpage for your shell should describe the builtins functions.