I think every RAW-converter or Photo-DAM-system like PhotoMechanic and iMatch prepare Thumbnails and bigger Previews too inadvance in order to make fast scrolling through wast amounts of picture possible.
The problems with the RAW-converters is that some even creates the bigger previews in advance like Lightroom does when you “Import” pictures and if they (often recommended are smaller than 1:1) they have to be scaled when the users starts to edit a picture
Photolab is a little different there and also creates new Previews when a folder is opened in a session. Also when a certain picture is clicked or stopped at both in Picture Library (try and se a little white “blipp” when you stop even there. In the Development-view it is the same when scrolling fast in the filmstrip and stops at a picture. Instatly it gets refreshed but the thumbnails is the filstripped are all cached for speed.
Also when we reindex a whole picture archive of tens of thousands of pictures it can take halv an hour or so with say 20-30 000 pictures and a great part of that time is used to process the pictures and create thumb nails and possibly even the previews in advance to gain speed when scrolling. These behaviors gets very obvious when you have a lot of pictures in a folder.
These limitations that stems from needing both thumbnails for speed and previews for editing is a problem för all RAW-converters and that is why an external DAM side by side with Photolab is so much faster to handle wast amounts of pictures. Some users have been using extrnal DAM-systems in parallell a long time especially with Photolab since it is working straight on the folders in the filesystem - others doesn´t do that - they have special Import/Ingest-procedures to improve speed.