Bash History not working as expected

> cat ~/.bash_profile
[[ -f ~/.bashrc ]] && . ~/.bashrc

> cat ~/.bashrc
#!/bin/bash
iatest=$(expr index "$-" i)

if [ -f /usr/bin/fastfetch ]; then
	fastfetch
fi

if [ -f /etc/bashrc ]; then
	. /etc/bashrc
fi

if [ -f /usr/share/bash-completion/bash_completion ]; then
	. /usr/share/bash-completion/bash_completion
elif [ -f /etc/bash_completion ]; then
	. /etc/bash_completion
fi

if [[ $iatest -gt 0 ]]; then bind "set bell-style visible"; fi

export HISTFILESIZE=
export HISTSIZE=
export HISTTIMEFORMAT="[%y/%m/%d %T %F] "

export HISTCONTROL=erasedups:ignoredups:ignorespace

shopt -s checkwinsize

shopt -s histappend
PROMPT_COMMAND='history -a'

[[ $- == *i* ]] && stty -ixon

if [[ $iatest -gt 0 ]]; then bind "set completion-ignore-case on"; fi

if [[ $iatest -gt 0 ]]; then bind "set show-all-if-ambiguous On"; fi

export EDITOR=nvim
export VISUAL=nvim

if command -v lsb_release >/dev/null; then
	DISTRIBUTION=$(lsb_release -si)

	if [ "$DISTRIBUTION" = "Fedora" ] || [ "$DISTRIBUTION" = "Arch" ]; then
		alias cat='bat'
	else
		alias cat='batcat'
	fi
fi

export CLICOLOR=1
export LS_COLORS='no=00:fi=00:di=00;34:ln=01;36:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.gz=01;31:*.bz2=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.avi=01;35:*.fli=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.ogg=01;35:*.mp3=01;35:*.wav=01;35:*.xml=00;31:'

alias grep="/usr/bin/grep $GREP_OPTIONS"
unset GREP_OPTIONS

export LESS_TERMCAP_mb=$'\E[01;31m'
export LESS_TERMCAP_md=$'\E[01;31m'
export LESS_TERMCAP_me=$'\E[0m'
export LESS_TERMCAP_se=$'\E[0m'
export LESS_TERMCAP_so=$'\E[01;44;33m'
export LESS_TERMCAP_ue=$'\E[0m'
export LESS_TERMCAP_us=$'\E[01;32m'

alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

alias ebrc='edit ~/.bashrc'

alias hlp='less ~/.bashrc_help'

alias da='date "+%Y-%m-%d %A %T %Z"'

alias hug="hugo server -F --bind=10.0.0.97 --baseURL=http://10.0.0.97"
bind '"\C-f":"zi\n"'

export PATH=$PATH:"$HOME/.local/bin:$HOME/.cargo/bin:/var/lib/flatpak/exports/bin:/.local/share/flatpak/exports/bin"

eval "$(starship init bash)"
eval "$(zoxide init bash)"

[[ -f ~/.bash-preexec.sh ]] && source ~/.bash-preexec.sh

> cat ~/.bash_history
...
#1718339259
sudo pacman -Syu --needed
...

> echo ${HISTTIMEFORMAT}
[%y/%m/%d %T %F]

As you can see although I modified HISTTIMEFORMAT to "[%y/%m/%d %T %F] " so that every command’s execution time would be logged, all I see are long numbers and a # preceding them. Is this expected behavior?

If you set HISTTIMEFORMAT in bash it will automatically append the timestamps to each command in standard Unix epoch format. Can you check if the number is in the vicinity of 1.7 billion?
It might be better for you to format the existing timestamps because it might be difficult (and storage inefficient) to revamp how they are stored.