The Envy 13 is also limited to 16GB of soldered RAM while the Slimbook can be upgraded to 64GB. The 15" version has a huge battery advantage over the Envys.
It's also worth noting that the pricing listed includes a 21% VAT. The pricing is more competitive once you take that into account.
You can get an Envy with a Ryzen 4700U (the 8-core 15W CPU), 16 GB of RAM, and a 512 GB PCIE NVM SSD -- for less than $900.