Sikorsky designs in particular tend to utilize numerous tapered roller bearings, which seem to be rather intolerant of insufficient lubrication relative to non-tapered versions.
What you note about tapered roller bearings is essentially correct. The sliding contact between the inner race shoulder and roller end faces generates quite a bit of heat, especially on high speed shafts. The main reason a pair of tapered roller bearings might be used to support a spiral bevel pinion is because it is attractive from a weight and packaging standpoint.
In the AHS paper I linked there is a table (table 7) showing scoring results from the trade study Sikorsky conducted comparing split torque and improved planetary designs. For the "technical risk - oil out" attribute, the split torque design scored 7.5/0.75 (raw score/weighted score) and the improved planetary design scored 5.0/0.50. A raw score of 10.0 is best and 0.0 is worst. So based on the results of this trade study Sikorsky seems to conclude the split torque design is superior overall to the improved planetary design in LoL performance.
One other interesting thing I noted about both designs described in the Sikorsky trade study was that they appear to use a duplex angular contact ball bearing/cylindrical roller bearing arrangement to support all of the spiral bevel pinons, rather than a pair of tapered roller bearings. The 3 bearing arrangement is larger, heavier and more expensive than a 2 bearing (tapered roller) arrangement, but it should perform better in LoL conditions.