less does not quit by q key before input ends, if it has not displayed full viewport of text

Test case:

{ for i in $(seq 10); do echo $i; sleep 1; done; } | less

Press q before left side of pipe has finished and less has not displayed whole viewport of text.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: less 487-0.1
ProcVersionSignature: Ubuntu 4.15.0-96.97-generic 4.15.18
Uname: Linux 4.15.0-96-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.20.9-0ubuntu7.14
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Apr 25 08:45:08 2020
Dependencies:
 debianutils 4.8.4
 gcc-8-base 8.4.0-1ubuntu1~18.04
 libc6 2.27-3ubuntu1
 libgcc1 1:8.4.0-1ubuntu1~18.04
 libtinfo5 6.1-1ubuntu1.18.04
InstallationDate: Installed on 2019-07-08 (291 days ago)
InstallationMedia: Xubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
SourcePackage: less
UpgradeStatus: No upgrade log present (probably fresh install)