I work on infrastructure for serving large language models but I don't have any background in ML, so my perspective is looking at these models as a black box (and also conversations with the people that do the ML stuff). It is the case in practice at least from a latency side that with a fixed context length N, embedding any number of tokens from 0 to N takes the same amount of time. Perhaps it's a difference between the conceptual and actual implementation on GPU?
edit - This occurred to me after the fact but I wonder if the difference is that the use case I work with is processing batches of many different embedding requests (but computed in one batch), therefore it has to process `min(longest embedding, N)` tokens so any individual request in theory has no difference. This would also be the case for Anthropic however.