The radio number listed in the OP is for the Sense 5 radio. So the OP must have flashed that radio separately from the 2.15 firmware package at some point, if they are on hboot 1.09 and have always been so.
If no signal drops of random reboots are experienced, there isn't a reason to update to the 2.15 hboot and associated firmware. Either you are in the population that simply does not experience that problem, or having the 1.31 radio has already resolved it. It has been suspected that the radio is the main culprit, but I don't think it was ever confirmed that flashing the Sense 5 radio (1.31) alone without the other 2.15 firmware solves the issue.
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Phone: HTC One X (AT&T version) Rooted, Bootloader Unlocked, S-Off
Tablet: Samsung Galaxy Note 8 (WiFi only) Rooted