Another team in my department recently hired a data scientist. I am the only one with any real data science training in our department and my manager asked me to have an informal chat with him to gauge the level of his knowledge and see if he can help our team as well.

Since he was already hired and if he did collaborate with us, it would have been on an informal "their team is doing our team a favor basis", I wasn't in a position to ask him pointed technical questions but instead I had to assess his skill level indirectly from the informal get to know each other meeting we had.

I asked him if he was comfortable coding in R, and he said yes, but he didn't know what RStudio was, which in the last 4 or 5 years has become the de facto standard IDE for writing R code.

Am I right in seeing this as a red flag?

I personally find it very surprising that someone who has been keeping up to date on the latest statistics and machine learning techniques in R, isn't aware of the IDE that everyone else is using, and I am tempted to go back to my boss and say that he doesn't know as much as he claims he does.

But I feel that I might be being too hasty in passing judgment.

Based on the answer and some of the comments I got, I need to clarify something: I don't expect him to be proficient in RStudio, if he's comfortable with another IDE or with command line, that's perfectly fine. In fact I would be impressed more by someone who doesn't use RStudio and uses the basic R interpreter or R Jupyter.

But not using the most popular IDE is one thing. Not having heard of it at all is another thing.

A Windows developer who doesn't like Linux is fine, a Windows developper who hasn't hear of Linux is alarming.