Command "look" misses some matched words

[Weller]

As we know, command "look" displays lines beginning with a given string, and the lines are from file "/usr/share/dict/words" by default.

Problem is
 - if we run "look a" or "look b", the result only contains words beginning with upper-A or upper-B.
 - if we run "look" for [c-z] like "look c", the result only contains words beginning with lower-[c-z].

Eg1:
    $ look a | tail
    Azores's
    Azov
    Azov's
    Aztec
    Aztecan
    Aztecan's
    Aztec's
    Aztecs
    Aztlan
    Aztlan's

Eg2:
    $ look c | head
    c
    ca
    cab
    cabal
    cabal's
    cabals
    cabana
    cabana's
    cabanas
    cabaret

As a result, "look b" never finds "byte", and "look c" never finds "CPU".

Please kindly check.
Thanks!

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: util-linux 2.37.2-4ubuntu3
ProcVersionSignature: Ubuntu 5.19.0-43.44~22.04.1-generic 5.19.17
Uname: Linux 5.19.0-43-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.4
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Fri Jun 2 10:06:16 2023
InstallationDate: Installed on 2022-09-29 (245 days ago)
InstallationMedia: Ubuntu 22.04.1 LTS "Jammy Jellyfish" - Release amd64 (20220809.1)
SourcePackage: util-linux
UpgradeStatus: No upgrade log present (probably fresh install)