It’s probable that Airbus has aligned its contaminated performance data with the requirements of CS 25.1591 which enables contaminant type and depth to be used in the calculations. However, if the reported conditions are poor (low coefficient) then the lower risk option is to land elsewhere or wait until the runway is cleared;- as recommended by UK AIC 86/2007 and AMC CS 25.1591 para 8.0.
Even if you could calculate the landing-distance in such conditions the margin of error, and thus risk, could be very high.
The example from Thunderbug appears to follow CS 25.1591 by stating that full reverse thrust is considered, i.e. no additional safety margin available from reverse.
However, it is surprising that without additional explanation, normal procedures and speed variation can be used. Para 8.3 of the AMC requires advice on approach speed increments above Vref, and if used, a distance correction should be provided.
An operator using actual contaminated distance with a 1.15 factor (as required by EU-OPS 1) might only have data which moves a theoretical minimum to a practical achievable minimum distance, i.e. there is no runway distance safety factor as for landings on non contaminated runways.