For now, yes, since Trunk currently links listings between sales channels via the SKU field. Don't worry, they don't need to be case-sensitive to match! And Trunk is smart enough to pick up and handle SKU changes so if you've already imported your listings, you can simply update the SKU on your sales channel's website/app and it'll automatically update within Trunk like magic.
If you're new to SKUs, they are identifiers for tracking your inventory internally. A manual linker is in the works so in the future, the SKU field won't be required.