The delta in performance is expected given the difference in specs between the desktop RTX 3080 vs the mobile version. The laptop version is not even running GDDR6X to begin with which itself will result in performance lost for a bandwidth hungry GPU. Might be interesting to see if TechSpot can get their hands on a Lenovo Legion 7 (16) with the full power (up to 165W) RTX 3080 16GB for testing, and to include RT performance.
Having said that, with most RTX 3070 and 3060 Ti being sold at insane prices, I think getting a mobile RTX 3080 may be the best way to get an Ampere card without paying tax to scalpers. Where I am living, the RTX 3070 are going for between 2.5 to 3x the launch day price. For high end cards from Asus, I.e. TUF and Strix, these may go even higher. With the higher TGP RTX 3080 mobile getting within striking range of the desktop RTX 3070 at 1440p, I think it could be a cheaper alternative to getting a desktop RTX 3070.