The limit is 100K nodes (as we see them) not neccessarily 100K nodes in the schema. See the explanation below:
The node limit applies to the total resolved number of nodes - not the number of definitions in the schema. For example, a schema might define element "X" and an attribute group which defines 10 attributes. The schema might also have 20 other elements which have "X" as a child and also include that attribute group. This would result in the "X" element creating 20 nodes and the attribute group creating 200 nodes (10 attrs x 20 refs). This means the 100000 limit is relatively easily reached for a schema described by what might look like a small XSD.