The query is not quite right. You can see this if you comment out the INTO line.
You are telling the engine you want everything from both drawings’ tables, wherever an object from either drawing touches an object from the other. Some objects might appear twice, if they happen to touch more than one in the opposite drawing.
All fields from A will be followed by all fields from B. There will be two Geom fields, with names made distinct by a suffix. And so on.
If you picked the right Geom field to make a new drawing from (the first one), this would sort of work, but not perfectly.
There are at least a couple of good ways to do what you need. The simplest is possibly a LEFT JOIN followed by a filter.
A.[source_id], A.[Geom], A.[example]
A.[mfd_id] AS [source_id], A.[Geom], A.[example],
[Drawing_A] AS A
[Drawing_B] AS B
ON GeomTouches(A.[Geom], B.[Geom], 0)
WHERE B.[mfd_id] IS NOT NULL;
A.[example] is a placeholder for any other field(s) you might need from A.
Then it is a question of sorting out a new drawing to take data from the new table.