what are the all bus types internal hard drives use?

Question

I have got a task of identifying external hard drive when it is connected. So, I decided to differentiate them according to their BusType, I am maybe mistaken I don't know (if yes, please correct me). I want to know if their Bus Types differ all the time, or most of the time and what are the bus types internals use and bus types externals use?

I type this command in powershell:

Get-PhysicalDisk | select Friendlyname, BusType, MediaType, DeviceID

and it gives this output when there is no external drive:

Friendlyname          BusType MediaType DeviceID
------------          ------- --------- --------
TOSHIBA DT01ACA100    SATA    HDD       0
HS-SSD-Desire(P) 256G NVMe    SSD       1

Now, this is output when there is External Hard drive:

Friendlyname          BusType MediaType   DeviceID
------------          ------- ---------   --------
TOSHIBA DT01ACA100    SATA    HDD         0
HS-SSD-Desire(P) 256G NVMe    SSD         1
Seagate Expansion     USB     Unspecified 2

So, externals always use "USB" bus type or not? So, am I doing right? Please help me out in this?