Odd behavior with yesno dimension

[ChrisB]

Hello!! I have a Looker report that uses a view. It relies on a derived table built thusly

view: cte_seller_revenue_past_12_months {
  derived_table: {
    sql: SELECT
        seller.id as seller_id,
        true as revenue_past_12_months
      FROM ...
      JOIN ...
      JOIN ...
      WHERE contract_entry.INCOME  > 0
      ...
      ...
      GROUP BY 1,2
      HAVING COUNT(DISTINCT (TO_CHAR(DATE_TRUNC('month', CAST(contract_entry.OCCURRED_TIME AS TIMESTAMP_NTZ) ), 'YYYY-MM'))) = 12
      ORDER BY 1 ;;
  }

The LookML has two dimensions

  dimension: seller_id {
    type: string
    hidden: yes
    sql: ${TABLE}.seller_id ;;
  }

  dimension: revenue_past_12_months {
    type: yesno
    sql: ${TABLE}.revenue_past_12_months = 'True';;
  }
}

When I add my `revenue_past_12_months` as filter, it behaves oddly. If I select NO, I would expect to retrieve 0 records but it does not work (I get data back). If I select YES, I get data back.

Looking at the SQL code for the report itself, I noticed the following

WITH cte_seller_revenue_past_12_months AS (SELECT
        seller.id as seller_id,
        true as revenue_past_12_months
      FROM ...)
SELECT
    seller.SELLER_ID  AS "seller.seller_id",
    seller.COMPANY_ID  AS "seller.company_id",
        (CASE WHEN cte_seller_revenue_past_12_months.revenue_past_12_months = 'True' THEN 'Yes' ELSE 'No' END) AS "cte_seller_revenue_past_12_months.revenue_past_12_months"
...
FROM DBT.CONTRACT_ENTRY_MART   AS contract_entry
LEFT JOIN DBT.COMPANIES_MART
     AS seller ON contract_entry.SELLER_ID = seller.MEMBERSHIP_ID
LEFT JOIN cte_seller_revenue_past_12_months ON seller.SELLER_ID = cte_seller_revenue_past_12_months.seller_id
WHERE ... AND (NOT (cte_seller_revenue_past_12_months.revenue_past_12_months = 'True') OR (cte_seller_revenue_past_12_months.revenue_past_12_months = 'True') IS NULL)
GROUP BY
    1,
    2,
    3
ORDER BY
    1
FETCH NEXT 500 ROWS ONLY

Why is Looker adding an OR (cte_seller_revenue_past_12_months.revenue_past_12_months = 'True') IS NULL  ?? If I remove it, the filter runs successfully.

I know I am missing something here. What do I need to do to make my filter work? Any advice?