I think that can be to compare only those crypto, which in than similar. But still, any crypto is individual. Therefore, you can only compare crypto in some similar parameters.
I think they have their own reasons for comparing those cryptocurrencies.
We are investing in volatile cryptocurrencies so we are mostly relying on the price changes, in order to know what is the better cryptocurrency to invest in, for the time being, they will be comparing other cryptocurrency's price changes over time to Bitcoin. We don't need to worry as we are all investors and I don't think we should fight for the differences in our investments, we should support each cryptocurrencies.