Is there any sound pedagogical reason for a time-limited examination (closed or open) at the undergraduate/advanced UG level ?
For many subjects, yes. For others, no.
I had an exam for a subject in school called "technical graphics". It involved drawing parabolas and projections and so forth on a big sheet of A3 paper with pencils and protractors and compasses. It was widely-regarded to be a subject of skill more than knowledge: the exam was timed and you had to accurately and quickly and carefully draw up four or five questions. A small inaccuracy becomes compounded through the rest of the drawing. Given unlimited time and some basic knowledge, nearly anyone could ace the exam since acquiring the necessary knowledge was easy; but acquiring the skill to do the timed exam was hard. And it was the skill we practised in class. Was this skill useful? Was it a learning outcome to draw quickly? I would say yes, of course; if I were to become a draughtsman (leaving aside CAD et al. for the purposes of the analogy), learning to draw quickly and accurately would be important to my livelihood. And it was the tightly-timed test that put emphasis on this learning outcome.
Likewise if I were doing a cookery lesson, cooking quickly would be important. If I were doing a programming lesson, programming quickly would not be as important, but it would still be important. And so we get into the usual varying shades of grey.
Generalising, we can define different types of learning based on the two main types of memory targeted: procedural memory (residing below the level of conscious awareness) and declarative memory (facts and/or knowledge that can be consciously recalled or inferred from other such facts/knowledge). Some subjects – like technical graphics or cookery or programming – put a strong focus on development of procedural memory alongside declarative memory. Other subjects – like biology or history – emphasise declarative memory far far more than procedural memory.
As such, I would say that the importance of a time-limited exam for a subject is correlated with the emphasis on procedural learning for that subject. A teacher may then wish to consider whether or not procedural learning is important for their subject or not.