They are in fact hard as dicks, I bored one out to use the standard 15mm/ 12pin bearing and it was definitely in the ballpark to run a bearing, HSS tool wouldn't cut it.
That engine never accumulated much hours but it didn't blow up, and I was sending it pretty hard, calculated 12k based on gps speed and gearing
I still think pressing in a a35 rod is way easier than all these shenanigans, and you know it will last.