As adding document into "Recent Documents" list requires creation of the thumbnail of the first page, I assume disabling this operation during loading of the file could speed up loading process of the document (time gap between when user clicks on the document and really could start typing in it in LO).
Initially document is added always during following document events: - SfxEventHintId::OpenDoc - SfxEventHintId::SaveDocDone - SfxEventHintId::SaveAsDocDone - SfxEventHintId::SaveToDocDone - SfxEventHintId::CloseDoc - SfxEventHintId::SaveAsDoc
Thank you for reporting this suggestion. I have set the bug's severity to "enhancement."
https://gerrit.libreoffice.org/c/core/+/90775