timeout hangs when combined with sudo and watch

[Mikko Rantalainen]

Command
$ timeout 15s watch -d date --iso=ns
works as expected and shows clock going forward for 15 seconds and then stops.

However, command
$ sudo timeout 15s watch -d date --iso=ns
hangs forever.

I'm not sure if this is a bug in sudo, timeout or watch but I'm reporting this as timeout issue because I haven't experienced similar problem unless I use timeout.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: coreutils 8.28-1ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-124.140~18.04.1-lowlatency 5.4.195
Uname: Linux 5.4.0-124-lowlatency x86_64
ApportVersion: 2.20.9-0ubuntu7.28
Architecture: amd64
CurrentDesktop: MATE
Date: Mon Sep 5 18:41:42 2022
EcryptfsInUse: Yes
InstallationDate: Installed on 2019-01-05 (1338 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: coreutils
UpgradeStatus: No upgrade log present (probably fresh install)