That may be true for most of it, but Data.Sequence has been using the Foldable defaults. That's going to change in the next version, but unless I goofed up the semantics remain the same.
On 2016-06-10 at 14:29:47 +0200, David Feuer wrote:
[...]
> 3. The containers package should be consistent with base in this regard.
for the record, `containers` appears to follow the new stricter
semantics for lists at least since 2014:
https://mail.haskell.org/pipermail/libraries/2014-November/024081.html