I believe it's to do with minimising the effect of a birdstrike.
Most aircraft I have flown over the last 23 years have had some guideline or other concerning birdstrike risk, although that was normally below 8000'.
EZ decided, about a year or so ago, to raise this to 10000' and introduce it as an SOP.
Don't know if the decision was based on any specific data.
Rates of climb and descent can be adjusted using V/S to eliminate nuisance TA/RAs but, if this is a big issue, why not write to EZ and seek clarification?