I got this reply from the developer on the occasional lengthy duration for importing a web page:

If there is a hiccup in the network or the server the page is on becomes
unresponsive, it can take time to import the page; the progress
dialog will be displayed during this time (and another import cannot be
initiated until it has completed/canceled). Importing a web page involves
retrieving the page's contents, including referenced pages on the same
site (for keywording) and images (for storage if embedding), which can
take time, depending on a lot of factors, including connection speed and
responsiveness of the server and the pipe in between. We have not seen
this process never complete, but if there is a specific web page where this
happens consistently, we can take a look to see if the problem is
reproducible, and therefore debuggable.

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If UR takes longer than ADM, it may be because of UR's automatic keywording that it applies to imported matter.

Stephen R. Diamond