Universal Credit, transitional protection, and maternity leave

Peaky

My wife and I receive Child Tax Credit. Under Universal Credit, we'll get significantly less than we do currently.

I've read a little about transitional protection. According to a briefing note from December 2012, one change in circumstance that will trigger an end to transitional protection for Universal Credit is "one (or both) members of the household stopping work".

My wife has recently started maternity leave. I understand from the HMRC website that under tax credits this doesn't count as a change in employment for the first 39 weeks:

You count as being in work for up to 39 weeks. This is the first 26 weeks of ordinary maternity or adoption leave, and the first 13 weeks of any additional maternity or adoption leave.

Am I right in thinking that if UC is brought in on timetable, then if my wife takes more than 39 weeks of maternity leave before returning to her current job she'll count as having stopped working, triggering a migration to Universal Credit with no transitional protection, but if she returns to work after 39 weeks then transitional protection will preserve the cash value of our current tax credits award?