Jan 2021. Here was the official announcement: https://dgs.virginia.gov/globalassets/business-units/do/documents/newsroom/dgs-to-install-fence-around-lee-monument-to-prepare-site-for-statue-removal.pdf

> The Department of General Services today will install fencing around the Lee Monument grounds to ensure the safety of visitors and workers as part of DGS’s plan to prepare the site for the removal of the Lee statue. As we await the resolution of legal challenges that have delayed the statue’s removal, DGS wants to be prepared to act quickly upon a final determination. The fencing is not intended to be permanent.

So ya it's there so they can act quickly to take down the statue...