Generally, lower-level cultivators could not gauge the cultivation base of higher-level cultivators unless they had powerful senses or the latter exerted their power.
On the other hand, higher-level cultivators found it very easy to detect the cultivation bases of lower-level cultivators. Their superior divine senses could see through the strength of their essence, energy, or soul.
As such, unless Vaan had a special technique to hide his cultivation, Second-stage Divine Warriors could easily tell that he was a Low-level Rank 6 in Body Refining, Half-step Rank 6 in Soul Forging, Peak-level Rank 4 in Energy Gathering, and High-level Rank 4 in Mana Forming.
Naturally, they would also only concern themselves with his highest level of cultivation, as this was the most "accurate" representation of his strength.
After all, one plus one did not always equal two in cultivation.