[mattlondon]

Not sure what dictionary you used, but this sounds highly irregular to me as a native UK English speaker. I've never heard of "fella" being used to refer to anything but someone of male gender.

That said, clearly our experiences and interpretations differ.

There is no right or wrong here. As such I dont think we can easily reason that they were using it to refer to generic group at all as clearly there is confusion and different interpretations of the word. Using "fellas" to address colleagues in an email (for example) that includes non-males may lead you to inadvertently offending people who share my interpretation of the word.

I think it would be better for everyone to just use non-gendered terms in the first place to avoid this sort of confusion and potential to give offense (e.g. "guys" is another loaded term: some people think it is non-gendered, whilst others think it is strongly-gendered - as such probably best avoided in a lot of situations).

Some alternative options that are non-gendered could have been "people", "applicants", or "potential employees" (and for the "hi guys"/"hi fellas" email opening you can just do "hi all" or "hi everyone")