In [my most recent challenge](https://codegolf.stackexchange.com/q/137846/55329), which was scored by number of languages in a polyglot [the following question came up](https://codegolf.stackexchange.com/questions/137846/polyglot-the-oeis#comment337682_137846):

> 
> Do different [..] implementations of the same language count as
>  different langauges ([...] like browser JS and
>  Node.js)?
> 
> 
> 

To which I couldn't find any prior ruling either on Meta or after a short search through other questions tagged [polyglot](https://codegolf.stackexchange.com/questions/tagged/polyglot "show questions tagged 'polyglot'").

So my question:  

**Is it sensible / should it be the default to recognize different implementations (with implementation-defined default extensions) as different languages?**

(please note: the "yes" answer to the above was my tentative, preliminary ruling until confirmed / revoked via this meta Q&A)