After some time with this change it seems like they implemented it as a way to curve people from entering g5 and getting consistent until about low-mid r40s. Or I suppose just preventing people from going straight to the next grade when they get the next tier of Scan ability. Basically even though I got Scans for both BTN and MIN at r38, there's no consistency at all in g5 when compared to the same item in g4. To reiterate I can get Silver Ore to be fixed in g4, heck I don't even think I have to pump VIT to do it (for g4 BTN all of my logs are fixed regardless of base STR); but the minute I try to go to g5 (with 128 alloted VIT) and specifically aim for, and subsequently get Silver Ore in my approach phase, it's all over the place!

My guess is SE needed a way to stretch out the time spent in earlier grades, perhaps to limit supply of some of the upper tier materials.