CTO of BitGo here. I wouldn't call this a bug, per se, but it's a known issue that we plan to fix. The BitGo API is agnostic where the change output(s) are placed -- this is just an issue with the client-side SDK.

The primary reason we haven't changed it sooner is that BitGoD (which Bitstamp uses), currently relies on the change output being last to determine which output of a transaction is change when listing transactions. This was needed due to missing functionality in our back-end transaction indexer which has been remedied in the last few weeks.

The other reason we don't consider it a huge deal is that, until there is much more adoption of multi-sig, it's still going to be relatively easy to determine which output is change (it's likely the only one that starts with a "3").