In NDISCOVER/Arima-Font#36:
Arima has a different set of conjuncts than Noto, actually the exact conjuncts required as in the Malayalam script reform issued by the government in 2022, so it is normal to encounter different renderings of the same character strings in Noto, as before the reform the amount of conjuncts to be in a font were (more or less) up to the designer.
Maybe Noto will be updated in the near future to account for this new script reform