Hi {AlexCox},
Thank you for reaching Microsoft Community and apologies for the inconvenience this has caused you.
May I know what Windows edition, version and OS build is your Surface Pro 7 running on?
Please try these steps below then test if the same behavior still occurs with Bluetooth connecting automatically even when in Sleep mode:
1: Disable Swift Pair
Open Windows Settings > Bluetooth & devices
Select Devices
Under Device settings, toggle off the Show notifications to connect using Swift Pair
2: Power Management
Open Device Manager
Expand Bluetooth
Double-click Intel(R) Wireless Bluetooth
See if Power Management tab is available
Check the box next to Allow this computer to turn off this device to save power
Click OK
3: Disable USB Selective suspend
Open Control Panel > Hardware and Sound > Power Options
Select Change when the computer sleeps
Click on Change advanced power settings
On the Power Options pop up window, expand USB settings
Set the USB selective suspend setting to Disable
Click Apply then OK
If still behavior is the same after those steps or those options are not available on the device, please try using Hibernate option instead of Sleep. See; Shut down, sleep, or hibernate your PC - Microsoft Support.
Kind re gards,
Marrion