how to save a stage / layer in python correctly when using stage?

[sanders3d]

I'm constructing scripts that creates different kinds of stages. But what I can get my head around is when saving out a stage vs saving layer.
Below is a script which is run twice. First iteration you only save the layer, the second time you export the layer. These yield two different results

import mayaUsd
import mayaUsd_createStageWithNewLayer

from pxr import Usd, Sdf, UsdGeom

#global values

for i in range(2):
    index = i
    name = f"test_asset_{i}"
    savePath = f"/tmp/{name}.usda"

    #step one, create the stage
    stage_shape = mayaUsd_createStageWithNewLayer.createStageWithNewLayer()
    stage = mayaUsd.ufe.getStage(stage_shape)
    root_prim = Usd.ModelAPI(UsdGeom.Xform.Define(stage, f"/{name}"))
    root_prim.SetKind(Kind.Tokens.component)
    
    #step two, save the stage
    rootLayer = stage.GetRootLayer()
    rootLayer.identifier = savePath
    rootLayer.Save()
    if index:
        rootLayer.Export(savePath)

first usd

[stan@lou-25]$ cat test_asset_0.usda
#sdf 1.4.32

def Xform "test_asset_0" (
    kind = "component"
)
{
}

second usd

[stan@lou-25]$ cat test_asset_1.usda
#usda 1.0

def Xform "test_asset_1" (
    kind = "component"
)
{
}

I find it a bit odd that rootLayer.Export(savePath) would be the same as stage.Export(savePath). And also that rootLayer.Save() actually creates a SDF layer file and not a USD file. It's a bit confusing and I would appreciate if you guys could give me any pointers on which behaviour you recommend for saving out layers. Doing it manually in the layer editor always creates sdf files.
If I skip the rootLayer.Save() step it looks in the layer editor that the layer is not saved.

I hope it make sense.

best regards
stefan