5 year old will only eat dinner out of his school tiffin box, holidays or not

School closed a month ago and he still wants his dinner packed into the steel tiffin, lid on, which he then opens at the table like it's a surprise. Rice in one section, sabzi in the other, no mixing. Our caregiver now packs dinner the way she packs his lunch. Harmless, I think, but does this stop on its own, or do I start serving on a plate again before school starts?