When a learner of English continues studying English, which of the following two will be attained earlier: precise understanding of meanings of word, or a fast reading speed?

I suspect that it's the latter, because the precise grasp of meanings of word would be, in general, more or less gradually attained by some mental calibrative process via many, many real usages of words.

In other words, I suspect that, as studying continues, generally a faster reading speed, as to temporal order, precedes a better, deeper understanding.

I think that it is somehow like seeing a dim view for you to read an English text with incomplete grasp of meaning of words, while native English speakers can see it clearly.