I was looking through my stables and checked my two ferrikkis stats and noticed their wild stat boosts have become zero, I know they must have had them since I caught them in the grove and seem to remember they did.
https://www.sylestia.com/view/pets/?petid=3829485
https://www.sylestia.com/view/pets/?petid=3837915

I have a lunemara who's wild stats are still in-tact that I caught yesterday, same day as the second one.
https://www.sylestia.com/view/pets/?petid=3836904

So it may be limited to only ferrikkis.

The Bonus Stats on Grove pets is related to their Trait Point count.
+0 = common
+~5 = uncommon
+~10, like the lunemara = is rare
+~25 = epic
+~40 = legendary
+??? = mystical

(unless it's an egg, in which case unthemed = 1 step below what the trait point count would be on a wild (epic = ~10), while Themed = 1 step above (rare = ~25))

They are both commons, so that would explain it, but I seem to remember them having wild stats before...
If I catch another common I'll check them more carefully. Thanks.

Seeings as I have several grove rarities, I can provide examples of
an uncommon ferrikki
a Rare ferrikki
and an epic grove pet

Those are all exacly within the ranges you mentioned, as is my rare lunemara.
It's possible I just got them confused with some other grove pets that actually did have wild stats.
There are certainly enough of them around.
Thanks for the helpful information!