There is no "standard" terminology but I would say small line count is a definite factor here. Small LOC count implies low complexity of integration and low risk. Risk? Yes, the smaller the codebase, the easier it is to take your own fork and maintain it, even if the original project is no longer maintaining the codebase.

Of these two low complexity is probably the main selling point.

Small also implies generally "an elegant engineering solution to a problem that generally may involve layers of accidental complexity" and hence also incites a sense of beauty. Aesthetics can be important for people that are hand crafting their codebases.

weight == resources (both in terms of RAM, code space, maintenance overhead, etc).