As long as Lin Zheyu doesn't take the initiative to reveal that he hasn't started Bone Marrow Cultivation, others cannot discern this solely by sensing his aura.
Logically, Martial Artists in the Bone Marrow Refining Realm don't need the Essence Qi Elixir to aid in refining Qi Blood.
Martial Artists in the Bone Marrow Refining Realm mostly use the Essence Qi Elixir as a recovery aid.
However, this usage is extremely luxurious.
In the Bone Marrow Refining stage, the main task is comprehending True Intent and integrating it into Essence, Qi, and Spirit Energy to evolve True Strength.
Only after evolving True Intent and when consolidating True Strength do they need the Essence Qi Elixir to supplement Qi Blood and speed up the consolidation of True Strength.
Lee Mengxi definitely didn't send the Essence Qi Elixir because he recognized that Lin Zheyu is only at the Qi Blood Realm level.
He did this primarily to show sincerity.
