Yes, but that was over a year after the signature above was was written. (And, in fact a mere six months before his death.) By 1940 he could no longer write without considerable difficulty, if at all, and he was consistently signing with a rubber stamp:
I have seen the signature you describe, and wouldn't be at all surprised if he had help moving his hand. (Photos taken of Gehrig at his Parole Board desk seem to show a great deal of hand paralysis,)
There are many letters of thanks written by Gehrig after "Lou Gehrig Appreciation Day," July, 4th, 1939. They are all signed by Gehrig, and signed well. During the 1939 season, his signature was
not a scrawl.