PBC, or prescriptive based compliance is allowable for contingency fuel planning if the Operator can demonstrate to the satisfaction of the Regulatory Authority that fuel is allocated as described in the Standards and Recommended Practices. (ICAO Annex 6)
The ICAO Document 9976, Flight Planning & Fuel Management Manual (FPFM) states:
4.18.6 An example involves an operator that does not carry five per cent contingency fuel exactly as defined in Annex 6, Part 4.3.6.3. An Authority may consider an operator in prescriptive compliance without the need for an operational variation if the terminology and contingency fuel calculation method used results in a demonstrably equivalent (or greater) amount of fuel. Conversely, an operator may be deemed out of compliance or require an operational variation if the terminology used is largely inconsistent with 4.3.6.3 c) and/or the calculation method used results in a lesser amount of fuel.
As your 6 minutes of contingency exceeded the typical ‘5% of trip fuel or 5 minutes at 1500’AAL’ fuel then you are in compliance with the regs based on PBC. I do agree however that an e-mail to ops would satisfy your curiosity, as technically they are not implementing what is documented in your OMA.