It is a well-established concept called https://www.investopedia.com/terms/s/sumofpartsvaluation.asp. A company's value is estimated on net present value (npv) of its projected, discounted future cash flows. If a company has a large, stable subsidiary that is growing slowly but is cash flow positive and a very fast growing but money losing subsidiary, it makes more sense to value parent company as if both subsidiaries were separate companies than the average of the two. A famous example was AWS within Amazon before it became noticeable in the bottom and top lines.