A trailing $match after $geoNear is currently not pushed down into the geo stage.
A $match after $geoNear stays in the pipeline as a separate DocumentSourceMatch stage. The pipeline optimizer (DocumentSourceMatch::optimizeAt) only seems to merge consecutive $match stages. It does not merge into a preceding $geoNear. The buildInnerQueryExecutorGeoNear path pops $geoNear from the pipeline front, leaving trailing stages intact.

The $match is then executed as a pipeline stage after DocumentSourceGeoNearCursor produces documents.
This could be optimized by pushing the trailing $match expression into the $geoNear stage.

For example, in the following query, the $match stage is not merged into the $geoNear stage.

const explain = coll.explain("executionStats").aggregate([
    {
        $geoNear: {
            near: {type: "Point", coordinates: [0, 0]},
            distanceField: "dist",
        },
    },
    {$match: {k: {$gte: 2}}},
]);