Shell Programming and Scripting

I remember having used that notation years ago at outsourcing service division of HP (don't remember the HP-UX version nor the Hardware on which it was) ... Or is it my brain which is betraying me ... already alzeimer ???
(a long time i haven't use HPUX)

If you used it on HPUX then that probably wasn't right. It is a quite common mistake, and often it does not get corrected, since the trouble is that it will only get noticed if there is an actual error message on stderr (and scripts do not always get tested properly). The only time one would use 2>&1 ... > is if stdout and stderr were pointing to different destinations before and you want to point stderr to where stdout is pointing before redirecting stdout to somewhere else.

I wasn't writting a script, i was fixing an existing script and the fix was to rewrite so.

So maybe it is my brain : i don't remember the exact context ... maybe the context was : an error unexpectedly logged into a log file ...

Oooops - good morning !

That would be the latter, welcome to the club
HP, like most others Unix vendors, is using System V ksh88 code (likely with custom patches). This code is processing the redirections in order they are found, like the traditional bourne shell, bash and all POSIX (more or less) compliant shells. Open Group: Shell Command Language (Redirections)
There is absolutely no reason for this standard way to be deliberately broken.
HP-UX: Command Separators

@jilliagre
Yep, i think i used it in a very specific context : the redirection were for sure working just the standard way. I guess it is just the expected result for that specific need that made me use the 2>&1 before, and it was so unusual and so far in my souvenir, this is what brought the confusion in my too little brain lol