Thank you for your quick reply.
I'll mail to API support .
this option was originally designed many years ago (I think it was 2006) when there were mostly single core CPUs in use. This allowed to use a single thread and so to load files faster (I hope I described that technically correct). Now in times of multi core CPUs obviously SOLIDWORKS loads the files even faster in most cases when this option is unchecked. So the comment "(faster)" was already removed in 2018 on that option and the option itself has been finally removed in 2019: http://files.solidworks.com/Supportfiles/Whats_new/2019/english/whatsnew.pdf#page=30
This option was added around the 2006 SP1 when SolidWorks implemented multi-thread loading of files.
One thread loads the display data (eDrawings\Quick View data) so users can spin their model around and such while a second thread loads the actual data for the part\drawing\assembly.
From 2006 SP1 release notes “You can reduce the time to load models by selecting No preview during open in Tools, Options, System Options, Performance. Selecting this option disables the interactive preview that otherwise appears while the model is loading.” (http://files.solidworks.com/Supportfiles/Release_Notes/2006/english/relnotes.htm)
Back in the 2006, multi-core processors were not the norm so this option was added to allow single thread loading for users with older hardware.
Today it is near impossible to buy anything less than a quad core processor making this option obsolete and worse, this option causes SolidWorks to take a completely different code path on File>Open resulting in many random\oddball SPRs. (400+ SPRs related\caused by this option)