(Not a bug) Redirection taking too much time

[pourko2--- via Bug reports for the GNU Bourne Again SHell]

echo $BASH_VERSION
5.3.3(1)-release

TIMEFORMAT='>>> real: %9R'
warmup () { local n=10000; while ((n--)); do :; done;}

warmup;  time { a=2 && b=5;}
>>> real: 0.000004

warmup;  time { a=2 && b=5 >/dev/null;}
>>> real: 0.000018