I don't think you can assume that exporting as a SVG will reimport back into Sketch the same way. Exporting to SVG is a lossy process and you lose a lot of information. For example, in your exported svg
<g id="mypage" stroke="none" stroke-width="1" fill="none" fill-rule="evenodd" font-family="PingFangSC-Regular, PingFang SC" font-size="24" font-weight="normal">
<text id="Test-Export-Svg-by-c" fill="#224B8F">
<tspan x="0" y="18">Test Export </tspan>
<tspan x="0" y="51">Svg by </tspan>
<tspan x="0" y="84">createLayerFro</tspan>
<tspan x="0" y="117">mData</tspan>
</text>
</g>
There are 4 text layers exported which is why when imported back into Sketch they become 4 layers. What are you trying to accomplish? I would recommend looking into another format for exporting your objects so that when you reimport them they can be properly parsed.