iPad not downloading original photos from iCloud

Similar case to this thread : iPhone not downloading photo originals fr… - Apple Community

Last week, I got my first iPad (iPad Pro M5 1TB), hoping to download all original photos from iCloud (total 344.86GB, 76,759 Photos and 2,310 videos). For a week's time, the iPad was plugged with original charger, and placed next to the router (download speed was >700Mbps). However, it downloads the original only if a photo is opened for editing.

I consulted Apple store staff two days ago. I was advised that it is not normal. And I should erase all contents, and reset the iPad without syncing settings from other devices (i.e. my iPhone). However, still no luck, no photos were being downloaded automatically.

Is there any other way to get iPad to download from iCloud automatically?

I have a genius bar appointment in two days. Hopefully we will find out a solution.

Otherwise I will be requesting a refund. Honestly, I am so frustrated and disappointed with the whole experience on iCloud and iPad. Thanks for your attention.