Hi Erik,
This is by design as you suggested.
All links sent through the Tweet Button will be turned into t.co links. When a tweet is delivered via the API to a client supporting [node:127], they have three versions of the URL denoted for them: the t.co version, the full URL originally supplied, and a “display URL” containing the ellipses at the end for efficient, tight display. The Twitter website leverages all this metadata to “unwrap” t.co URLs for display.