Delete ignores constraints

I’m using two tables, Products and Categories, where Product belongs_to Category and Category has_many Products. When attempting to delete a Category, I check the associations with Ecto.Changeset.no_assoc_constraint(:products). The resulting changeset correctly contains the following constraint:

[
  %{
    constraint: "products_category_id_fkey",
    error_message: "are still associated with this entry",
    error_type: :no_assoc,
    field: :products,
    match: :exact,
    type: :foreign_key
  }
]

Here is the problem: when using Repo.delete(changeset), I see the exception (Ecto.ConstraintError) constraint error when attempting to delete struct instead of the changeset with a constraint error. Why so? (I’m using Sqlite3)
Thanks!