Related query - Are those slots in the spars for undercart bay sides?
Personal account - That same Revell Dambuster tool was my first "heavy", about 10 years before you indicate!
Yes they are and need to be handled with care at this point. The slots in the fuselage a very tight and need a file otherwise you can snap the spar an one of the slots (I did, but managed to fix it)
The Revell Dambuster Lanc was a kit my elder Brother started and gave up on - to fiddly for him ;)
With regards to Uncle Pete's query about when Airfix started putting spars in wings, I think it was when they started retooling kits - it's certainly a much better set up than the tab and slot.