Moving the bit about the scope of the role (jr vs sr vs lead) up to preface the rest of the comment would've toned it down a bit, but even there I disagree with the "taking a risk" part - a senior candidate shouldn't feel like it's risky to offer alternative perspectives. If I got the impression that the hiring manager thought asking questions would likely be a sign of "cannot focus on the task at hand," that's going to set off my own flags a bit.

If you're married to your interview process I'm worried you'd be even more married to your day-to-day process, and I haven't met a perfect company yet, so I consider being overly adherent to process instead of results a warning sign.

Also, as an interviewee, you stand to learn a lot more from that interaction than by rejecting it. Hell, I welcome coding challenges as an opportunity to size up the interviewer's chops!

If the challenge is conducted in a reasonable way, it should feel like any other design/pair programming session you've had at the office, and it can be quite revealing of the tendencies of your potential colleagues.

  > Also, as an interviewee, you stand to learn a lot more
  > from that interaction than by rejecting it.