I wouldn’t be so strict in the answer. You would need to know what you are doing according to the specific project.
Indeed would be a mistake use an avarage on a L2A scene; at the same time I would not be so restrictive using a First or Last approach in that specific case.
For L1C the situation should be solved using an algorithm that fits best the purpose (min/max/avarage…)
Thanks to the really interesting and well done notebook that you shared few weeks ago my attention has been focus on the metadata from the AWS products. ‘OVR_RESAMPLING_ALG: AVERAGE,’ is reported in a L2A product. I’ve been searching for a little in the documentation but I’ve not been able to fid anything regarding this. Maybe you have more info on this.
For sure, if that would be the algorithm, I would not be too happy as L2A is a BRDF correct and in my application would be better to have original values (First/Last alg.).