The 15-inch Laptop 4 has distinct battery, SSD and charging-port guides rather than sharing the 13.5-inch parts.
What to check before buying
Battery and storage
iFixit documents the battery and SSD separately for the larger Laptop 4. A storage upgrade and a battery replacement involve different assemblies.
Charging and fit
The Surface Connect port has its own guide. The 15-inch version's feet, screen and speaker parts should not be inferred from the 13.5-inch model.