On 2020-12-10 2:18, JF Mezei wrote:

Based on the NASAspaceflight guys, the 3 engines aren't enough to launch
a fully fueled Starship. This was likely the reason they had to scale
back from 15 to 12.5km because it would have required too much fuel at
liftoff and not enough power.

Another likely explanation I've seen is that they wanted to avoid
high-altitude winds at the transition from nose-up to belly-flop.

I don't think they would need to fully fuel the Starship just to reach
15 km altitude at low speed.