The entire process of fundamental investing is based on subjective interpretation.
You should read Aswath Damodaran’s Narrative and Numbers to understand how narratives shape valuations and numbers.
Why Usha Martin? We can question any company that has say a PEG > 2 or 3. But the market has continued to do that for years. See DMart, Astral, Nestle, Asian Paints, Pidilite and many others.
Valuation is not a science. It is based on the narrative. Instead of arguing with the market, it is more important to observe what it is trying to teach us. Over time, as market participants, we make money based only on the price. So, ultimately, the final arbitrator of all debates is price. And time also is a fluid concept. For a day trader, it may be a few mins to a few hours; for a swing trader a few days to a few weeks and so on.
For a long term investor, 1-3 yrs is a reasonable timeframe. So, keep this thesis and revisit it every year for say three years and see if your analysis was right or wrong. That way you will learn more about practical valuation than debating here on valuations with other forum members, who will possibly have their own narrative in mind.