Thanks for the heads-up about H3 making it relevant.
IIRC the GND TEMP prompt appeared on INIT A circa 2017. My current operator has around 40 ships and I am the only one making the entry because of long-time IT affiliation (garbage-in & garbage-out) and a borderline healthy dose of OCD. However, when asked, until today I kept telling dear colleagues that it does not make much of a difference, and they may decide to ignore it to avoid awkward stares from the other captains (and trainers).
Of course, a demonstration of the delta_ISA blending from Ground OAT value to the predicted air-mass value within the first 5000-ish feet of climb (AAL) is duly made afterwards. Hence my persuasion is the entry only fine-tunes the initial climb, which is messed up by the THR RED / ACC / initial SID climb / TMA ATC constraint limits anyway - and as such omitting the value during FMS setup bears causes no harm on any single individual sector.