Depends on the particular action IMO. I think for example the 99 Savage is quite thin in places, and can be prone depending on the user. But when you look at the number of them out there, and the shape they are in, it doesn't hold true.
The Winchester Lever guns, Marlins and other guns such as some pump guns are certainly prone to chipping at the tang. But look at how many Lee Enfields are out there with their two piece stocks without issue.
Some bolt guns have been known to break at the magazine well too.
Lots of variables, the user being the biggest, but stock design, wood grain etc play a part.
Overall I'd say yes, they are, but not as a huge issue.