The autocomplete component starts matching as soon as the first character is typed; it’s unlikely this will ever by very useful. With large data sets, matching can be very slow initially - because of the large number of matches - to the point that using this feature may not be feasible.
If it were possible to choose at what point the matching starts - eg after the first 3 characters are typed - it would make the feature much more useful generally - particularly for large data sets.
Even for large data sets, the matching can be very quick. Eg if a word is pasted into the autocomplete input, matching is instant; typing the same word may take several seconds.