Hello @Oleg and welcome to the forum!
I think the compact command does not force a compact, but is like the usual auto-compact which does compact only if configured parameters call for it. See my first link, and this example of forcing compact.
Does that mean you set an extra-large remote volume size (–dblock-size) on the job’s Options screen? Choosing sizes in Duplicati gets into that. A large remote volume size can mean slow restores especially when a file’s incremental changes get spread across a number of large files that need to be downloaded.