In your situation there is no hazard but the rule is there to cover all the different scenarios. I would comply exactly as Roger suggested. Why bother with parallel if the load is 60 amps unless voltage drop is an issue.
I thank all of you for your replies. The Handbook language gives me the sense that the Committee understood that the risks went up as conductor size went down, but that they drew the line at a point where it seemed no one would have a practical or economic reason to parallel conductors smaller than 1/0 copper. The handbook makes the same kind of remark with conductors larger than 1000MCM. No physical research results are cited to support the 1/0 minimum.
Why bother? Voltage drop is not the issue. I agree that if safety now or in the future is the issue, the Code is the Code and money cannot be the obstacle. Tragedy is always more expensive. But if safety is not the issue, as I sincerely think in this case, then approaching the AHJ for an exception is reasonable. It may not be approved because the AHJ is wary of setting precedents or other reasons. But am I being financially responsible if I do not ask, making a case based on more general principles of conditions of maintenance and supervision, qualified personnel, 24 hour supervision, industrial location, ampacity of a single set, amount and stability of the load, use of a plaque, etc? I am posting to get your views on when an exception might be sought and on what basis. I may sound cheap, but such are the times, and the cost of changing out a 22kA breaker and pulling out a set of conductors still gets my client's attention. Thanks again for your time.