If you do not run the same sequences, you do not know. Note I do not know what exact sequences you have tested, I write with only what I have read as as input.
I ran this on both versions on fresh instances / clusters with the data from a previous run :
\timing on CREATE TABLE gist_fastbuild(pt point); COPY gist_fastbuild FROM '/tmp/gist_fastbuild.copy'; CREATE INDEX ON gist_fastbuild USING gist (pt); VACUUM ANALYZE gist_fastbuild; \di+ gist_fastbuild_pt_idx
EXPLAIN (ANALYZE, BUFFERS) SELECT pt FROM gist_fastbuild WHERE pt <@ box(point(.5,.5), point(.75,.75));