Download station is a Synology specific piece of software, so no other NAS brand would have that, although some have some kind of variant of it. I have never used any of the NAS specific download apps, but as of right now, it’s not something Ugreen offers.
As to whether or not Ugreen will offer that in the future, that would be a question for their support and/or the official forum.
Also note that there’s a Pro version of the DXP4800 launching later this month, that has slightly more up to date hardware for US$40 extra.