After WWII there were large quantities of high quality German manufactured weapons and ammunition available in Europe and plenty of people willing to deal in them. The Israelis had cash and needed weapons. They were also desperate and took a very pragmatic approach, learned the hard way, to their own survival. They may also have taken some satisfaction in defending themselves using weapons made by their most industrious oppressors.
I have had three 7.62 X 51 Israeli Mausers since 1985 and have shot .308 soft point and FMJ from various reputable manufacturers and some real horror comic 7.62. The worse was Persian which grouped into 2 inches at 25 yards.
If your gunsmith says the rifle is safe I would not worry. You are unlikely to have problems if you shoot decent stuff.