Bruce,
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There a few things that I think work to mitigate the concern of the leads coming out of the socket, besides the significant force of friction because of the tight fit of the lead in the socket.
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The BS170s are held captive so there is not the part mass in concert with vibration to work the part out of the socket as is the case in examples presented.? The lead and bend help to mitigate thermal expansion.? As the leads warm up they expand a little.? Since the body of the BS170 is held in place the lead expansion likely puts some horizontal force and friction againt the socket.? A thermal spring if you will.??
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This is a hobby and not a space electronics reliability thing.? Based on the experiences that have been reported, it is more probable that a BS170 will fail due to overstress misadventures than the socket implementation.? ?Off to do a tin whiskers analysis on the QMX :-).
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Brien??
Brien - KE7WB