I've been using Osmo oils. This top oil and also their butcher block. Besides what they say that it is food safe, would this be fine for utensils which may get exposure to cooking temperatures ? Whether mixing soup or stir fry ?

https://osmo.ca/product/topoil-high-solid/

Osmo topoil is actually mostly what it says on the can - wax + oil. The wax part will melt/degrade very quickly at cooking temps. the oil portion will not.

If you are exposing it to cooking temps, and want something very natural, i'd just use an oil and not a "hardwax". The wax part is not going to buy anything.

"hardwax" is just a made up term that means nothing for real, some of them are harder waxes (carnauba), some of them are not. In any case, none of them will survive heat, because the wax won't.