For localized subtitles, please use the Dialogue system. It is not yet complete, but it is at least as functional as the Sound system. Dialogue Wave text is gathered for localization and the localized text will be used. The Dialogue system presents a specialized workflow and pipeline for spoken dialogue to be localized, both in terms of subtitles and in terms of (eventually) playing localized sound files.
As for the literal text not being gathered from your blueprint, I made a very quick test case here (master, not using 4.4) and found no issue. I’ll edit this post when I’ve tested using 4.4 from Github.
Update: Tested with 4.4 from GitHub. The behavior was reproduced. Some change after 4.4 fixes the issues. I’ll try to track it down.