Don't know how to work it out exactly, but 5.8% would be roughly equivalent to 3.3 deg GP assuming continuous RoD rather than descent at FAP. This is the thing, the minima for non-precision is calculated so that you can if you wish descend straight to MDA (1100ft) at 7DME and still maintain obstacle clearance, which in this case is 246 ft(75m). If there are no obstacles closer in, and there is sufficient room on the airfield to install ILS LLZ and GP, then you might be able to get down to Cat 1 minima. This would also require terrain clearance for a missed approach climb gradient of 2.5%
BOAC: just quoting ICAO re the GP angle, the French may have a 'difference' filed with ICAO.