If Lucifer acts overtly or covertly Uriel is empowered to act, but Uriel can choose the manner and time of that help.
Lucifer expended enormous energy in creating the spell which captured the Archive. Gifting Harry with Soulfire is seen to match that enormous expenditure. However that use of Soulfire is over time, is still paying back and will to the future. Harry used only the smallest part in rescuing Ivy, and yet Harry still prevailed, and still has access to Soulfire, which is why Harry is now a target of Lucifer. Lucifer made a mistake and Uriel exploited it in a fashion which is ultimately going to cost Lucifer going forwards far more than his own actions obtained any benefit.
Harry as a Starborn may have been a legitimate mortal force multiplier for Uriel to play giving back 100 times or more the initial investment. So far it has resulted the saving of the Archive, the extinction of the Red Court, the capture of the Titan and strengthening of the Accords. A whole list of unintended consequences. If Harry is turned Lucifer gets that force multiplier going forward. Not worked so far.