This is something Grindstone himself has and passes along. I’ve seen it in many from the line. It’s easily disguised in “good” pictures, but it’s there. I’ve attached pictures below where it’s visible to some degree.
Grindstone: [ATTACH=JSON]{“alt”:“Click image for larger version Name: IMG_8518.jpg?format=750w.jpg Views: 1 Size: 29.4 KB ID: 9833461”,“data-align”:“none”,“data-attachmentid”:“9833461”,“data-size”:“full”}[/ATTACH]
Birdstone, by Grindstone: [ATTACH=JSON]{“alt”:“Click image for larger version Name: GaineswayConformation_0.jpg?GapuZZEQn2AWegf3HgNZQPzIcJE2R1NP&itok=hd_Wzqd7.jpg Views: 1 Size: 15.8 KB ID: 9833462”,“data-align”:“none”,“data-attachmentid”:“9833462”,“data-size”:“full”}[/ATTACH]
Birdrun, by Birdstone: [ATTACH=JSON]{“alt”:“Click image for larger version Name: aae3052274fe470fbfb0d3245b1ce479.jpg?preset=default.jpg Views: 1 Size: 59.5 KB ID: 9833463”,“data-align”:“none”,“data-attachmentid”:“9833463”,“data-size”:“full”}[/ATTACH]
Summer Bird, by Birdstone: [ATTACH=JSON]{“alt”:“Click image for larger version Name: 3930292668_f8b620c2b1.jpg Views: 1 Size: 27.3 KB ID: 9833464”,“data-align”:“none”,“data-attachmentid”:“9833464”,“data-size”:“full”}[/ATTACH]
Not all of them inherit it, but it seems to be very common. I can’t answer your question whether or not it’s career limiting; all of the horses above were wildly successful racehorses. I tend to find the Grindstone line less durable than average. Then again, horses don’t read their paper, so you always have to evaluate the horse in front of you.