I am working with a table that has about 200 records. It previously had no index or constraints. I added PK/Clustered index on a unique column that is of datatype
SQL Server applies no smarts whatsoever to allocating pages. Probably, the table is 1-10 pages in size and these pages happened to be spread across some free space holes. SQL Server has no facilities to avoid this. It does not try to collocate related pages.
Fragmentation is nearly irrelevant for small tables since they usually end up being cached. These pages are never read again from disk.
Just for fun, you could likely avoid this by rebuilding the index over to a fresh filegroup with
MAXDOP = 1. The FG is empty so there are no freespace holes.