Its flavour can range from very sweet to very sour depending on the variety and ripeness.  

Apples can be  supporting for heart health, aiding weight management, lowering the risk of type 2 diabetes, and improving gut health through fiber and antioxidants.  

It tastes sour, acid,  bitter because of their rind, fresh, zesty, floral and herbal.

Lemons have Vitamin C for immunity and collagen production, aiding digestion with citric acid as well as they can prevent kidney stones with citrate, and improve iron absorption from other foods. Also they can support heart health and promote hydration.  

FACT: Lemons vs Lemongrass:

1) Lemons are a tart, acidic fruit from the Mediterranean, used for their juice and zest, but...

2) Lemongrass – it is a tropical herb with a milder, grassier citrus flavour used in Asian cooking;

My conclusion is that lemon must be more expensive than lemongrass. To knock down on production prices, bearing in the mind that a manufacture still want lemon flavour and what is more, they want this brew call as lemon involved brew, they use lemongrass instead of lemon.

It is resulting the they lose the quality of aroma and flour that the consumer might expect.