The two tree rule comes from AFAG and I feel in this situation, from what you describe, it is being implemented in its literal meaning more than likely by individuals not familiar with or from a practical arb / forestry environment.
In my view, working as a party of two in this aspect would be acceptable, as only one felling operation is being undertaken. This is the critical part. Two felling operations in the same area need to be a minimum of two tree lenghs. You are working as a team of two undertaking one felling operation at a time. Personally I would prefer this rather than two individuals working possible several hundred yards apart. This could be classed as lone working. I would detail this on the site specific risk assessment. Hope this helps.
