You would also need to unset HISTFILESIZE, export PROMPT_COMMAND="history -a", export HISTTIMEFORMAT="%d/%m/%y %T ", and set up log rotation to get the behavior listed in the article.
I have many shells open at once, sometimes dozens. Only one of them "wins" when saving history. If Bash has out-of-the-box support for merging multiple shell history, it's not obvious in the man page. And I have them open precisely because they're different contexts and I don't really want them sharing history. If you want a log of everything you run, you need to make it some other way.
So, basically, in combination with sp332's and raldi's points, the answer is that it is completely not the same.
I took the bash-history related stuff from https://github.com/mrzool/bash-sensible and have been VERY happy with it. Among other things, it makes sure all your histories from various open terminals get merged, not overwrite each other -- I think maybe just `shopt -s histappend` is enough for that? But I was messing around with my settings regarding history settings for a while tweaking and tweaking, until I found bash-sensible, tried it out cut and paste, and found it was perfect.
## SANE HISTORY DEFAULTS ##
# Append to the history file, don't overwrite it
shopt -s histappend
# Save multi-line commands as one command
shopt -s cmdhist
# Record each line as it gets issued
PROMPT_COMMAND='history -a'
# Huge history. Doesn't appear to slow things down, so why not?
