->with() query not working; can't figure out why

I'm struggling a bit, here: I can't figure out why this Eloquent query isn't automatically including my images relationship.

Here's the relationship:

class ImagesetCrop extends Model {
    ...
    
    public function images(): BelongsToMany
    {
        return $this->belongsToMany(File::class)->withPivot('height', 'width', 'left', 'top');
    }
}

And here's me dumping out the SQL to figure out what's wrong:

dd($this->resource->crops()
    ->with('images')
    ->orderBy(DB::raw('CONCAT(width, "x", height)'))
    ->toRawSql());

The SQL I get back from that dump contains nothing, at all, about including the images in the query as well:

select * from "imageset_crops" where "imageset_crops"."imageset_id" = 'fc7c4512-1c59-4701-a55a-01fe2e924b05' and "imageset_crops"."imageset_id" is not null order by CONCAT(width, "x", height) asc

Honestly, I just don't know why it isn't working. I must have written hundreds of Eloquent queries like this before. Am I just stupidly overlooking something?

EDIT: Annoyingly, it actually works fine in the browser. It's only in test-land that the eager loading doesn't seem to be working at all.

2ND EDIT: After loads of of debugging down to the simplest version of the problem, still no answers.

$imagesetCrop = ImagesetCrop::query()->with('images')->first();
dd($imagesetCrop->images);

The above code dumps out an empty Collection. However:

dd($imagesetCrop->images()->get());

That code brings back the expected Collection of File models. So it's specifically and only the eager loading that is failing, for some reason.