I think this is proving less true than expected, because Chip & Signature cards are widely issued outside the USA and transaction processing equipment recognize such cards. We have several reports of Chase cards accepted at unattended points of sale.
Do we? Perhaps I've missed these. I have seen a few examples where C&S is accepted at stations that are also known to accept mag stripes (London Tube, etc). Do we have any examples of C&S being accepted at unmanned POS that are known not to accept mag stripe (Amsterdam trains, Paris bikes, etc)? I very well may have missed these.