TabNine will still work on projects of 15MB or more, it will index the 15MB of files that are most relevant to the files you are editing (determined by distance in the directory tree).
The limit exists because otherwise latency or RAM usage might be too high.
A configuration option would indeed be nice. I have more than enough memory for tools providing a high value for my daily work. Kudos for setting same defaults!
The limit exists because otherwise latency or RAM usage might be too high.