The loadChunk(x, z, false) API, which is intended to load chunks successfully only if they are fully generated, appears to be successfully loading partially generated chunks (making them fully generated, and causing adjacent chunks to become 'more generated' - that is, following the progression of ChunkStatus from EMPTY towards FULL).  Unfortunately, this kind of defeats the point of 'generate=false', particularly for plugins like dynmap (and probably WorldBorder) that use generate=false to find defined/generated chunks without causing unbounded world growth.  I've given the code a look, but haven't been able to run down the root cause yet - I believe the fact that the 'ProtoChunkExtension' check drives a FULL load (same as generated=true) is a likely factor, but I haven't been able to find a logic change to avoid the behavior (e.g. only doing the load FULL is the ChunkStatus of the proto chunk is FULL).  Will keep looking on my end, as time permits.

I've got a temporary workaround for Dynmap - not a good one, but it sidesteps at least the worst of the issue, by checking IsChunkGenerated() in a 4 chunk radius around a chunk and only doing the LoadChunk if that is true for all chunks around the chunk.