Assessment periods and absence abroad

If a person travels abroad (and the trip is planned to exceed one month) is disentitleemt to UC for the whole of the assessment period in which they leave the UK,or is it apportioned?  I rather fear it is the former as although reg 11 does not mention assessment periods, the only reference I can find to apportionment appears to be in regs 21A and 22A, which apply to very specific situations.

All the assessment period unfortunately

Neither of the very specific apportionment circumstances apply, so usual rule in Sch 1 Para 20, UC PIP JSA ESA (D&A) Regulations applies:

20.  Subject to the following paragraphs and to Part 4, in the case of universal credit, a superseding decision made on the ground of a change of circumstances takes effect from the first day of the assessment period in which that change occurred or is expected to occur.

This also of course happens where absence is not initially expected to exceed (eg)1 month but then there is delay in returning, resulting in an overpayment for the initial AP.