Try explaining both indexing behaviors to a newcomer and you'll see the
difference.
Old behavior: `3:3` causes the dimension to be retained; `3` causes the
dimension to be dropped if it's a 'trailing dimension' (all the later
indices are also scalars) but retained if it's a 'leading dimension'
I am largely a fan of Matlab-idioms, but repmat is an exception, it leads
to code that only the person who wrote it will understand (at least for a
few days after they wrote it)
As someone who has never used repmat, I can't comment on that, but the
"automatic squashing" makes perfect sense to me. The first syntax
simplifies the structure down to a 1-D instead of a 2-D array with only one
row (repmat aside, why would I want to keep the extra dimension if it
doesn't
