Thank you for that. Could you provide the more correct Sanskrit word used for sentient being?
the standard word for "sentient being" in Sanskrit, there is nothing more correct. The point of the quote is that although the word sattva can be analysed in terms of a verbal root and a secondary suffix, the meaning "sentient being" can't be derived directly from the meaning of its grammatical parts; it's a purely linguistic convention.
In technical terms, Devendra is saying that the word sattva for "sentient being" is yaugikarūḍha, not yaugika. This gets into the Sanskrit grammatical theory of word meaning, which would take some time to explain.
Why in English do we use the word "sentient?" That implies feeling, which is not exactly the same thing as the mind. And even Buddhas have mind-phenomena and feeling-phenomena, but they are not conditioned by them. So I wonder if the Tibetan word sems has a somewhat different meaning than our English use of "mind."
The Merriam-Webster definition of "sentient" is "responsive to or conscious of sense impressions", which in both the basic 12-fold links & more complex abhidharma analysis is a central feature of what it means to "have a mind". Feeling (vedanā, tshor ba) is always a pleasurable, painful, or neutral response to contact (sparśa, reg pa) with a sense object. In Buddhism mind is nothing other than a stream of self-perpetuating responses to sense impressions.
Whether Buddhas have sense impressions was a controversial issue in some circles in India, but in Tibet the mainstream position is that Buddha activity unfolds effortlessly through the power of past aspirations.