It's not clear from this bug report, but it's very likely that the selected time zone was London. According to the Olson tzdata, London was in GMT+1:00 from 1968 Oct 27 00:00 (until 1971 Oct 31 2:00), which transition means that it didn't go back to standard time. The following is the Olson tzdata. (Refer to the zic man page on Solaris or Linux for the zic file format.)
# Zone NAME GMTOFF RULES FORMAT [UNTIL]
Zone Europe/London -0:01:15 - LMT 1847 Dec 1 0:00s
0:00 GB-Eire %s 1968 Oct 27
1:00 - BST 1971 Oct 31 2:00u
0:00 GB-Eire %s 1996
0:00 EU GMT/BST
Until 1.3.x, Java didn't support any historical (future) time zone changes, but it does since 1.4.0. The 1.4.0 output correctly represents the historical time zone (GMT offset) changes. However, the Java time zone system doesn't support time zone name (abbreviation) changes. "GMT" should be "BST" for the time stamp of Date.toString().
Around Windows NT/98/2000, there were some confusions with the GMT time zone (GMT vs. London). The recent Windows has more decent time zone support.
I'd suggest this CR be closed as Not a Defect.