After all, it is well known that the End of Dharma Era is somewhat different from a completely magic-depleted environment. Sometimes the End of Dharma Era does not mean a complete absence of Spiritual Energy, but rather a significant reduction in the concentration of Spiritual Energy in the air.
For example, it's like the oxygen molecules used to maintain survival in the air have greatly decreased. In such situations, large individuals might suffocate to death due to not being able to absorb enough oxygen molecules in time. Cultivators are similar in this regard; when the Spiritual Energy they rely on for survival dwindles, they can only passively head towards extinction.
Even though the concentration of Spiritual Energy is reduced, there's still a tiny bit remaining. As long as one can expand the range of absorption, they can still extract a certain amount of Spiritual Energy for self-restoration.
