I'm not sure where you picked this bit of trivia, but it doesn't have much basis in actuality. Track width is set by the NAB standards or which ever set of head type you have (DIN, etc) Extended LF is mostly about contour which has no bearing on S/N.
Now it is true that some people do not like the extended freq head, its not because of loss of S/N. They measure quite well in that regard, and as to low end response I have measured flat response to 17hz on an ATR 102 I restored for a client. Top end was extended out to around 34kHz (slightly down) at 30ips.
Personally I didn't hear any problem with the heads, quite liked them.
Alan Garren