Hi Sprout,
If you want import routes to the Level-1 routing table, you must add the parameter level-1.
isis 2
import-route isis 1 level-1
For details, please refer to:
https://support.huawei.com/hedex/hdx.do?docid=EDOC1100109721&id=EN-US_CLIREF_0172379574&text=null&lang=en