You have to look it from the perspective of OneDrive (the actual sync tool): If OneDrive detects a new file or a change in an old file, it starts its syncing process on this individual file. If the file is small, OneDrive doesn’t have to sync much. If the file is huge (e.g., a 10 GB container), OneDrive has to do a lot of syncing.
Your other question reminds me of this and it might answer your question: Using an External Hard Drive with Cryptomator - #4 by overheadhunter