<conjecture>The following is nothing official, or even proven, but the H20 had an issue with OTA whereby PSIP data would cause the reboots, since the HR20 is likely just a H20 in that regard (OTA circuitry/firmware), they probably preferred to leave it disabled until a proper firmware fix could be rolled out.</conjecture>
And let's be honest here, if they HAD released it enabled, and it rebooted like the H20, everyone would be posting "Why did they release it with OTA if it doesn't work!", or if they had waited to release the HR20 until the OTA was fixed, everyone would be posting (more of) "They lied to us about the date the HR20 would be released", so they are damned if they do, damned if they don't.