In my testing
ODBC connection to Postgres v11
Create a passthru query "SELECT COUNT(id)::INTEGER AS counter FROM foo"
Mark query as returning records
Open ADO recordset on above query

Result:
rs.Fields("counter").type = 20 ' DECIMAL ?!
rs.Fields("counter").value = ""

Same error with "SELECT COUNT(id)::BIGINT AS counter FROM foo"

Current state:
Have to revert MSO on 20+ backoffice client machines and hope that ADO will be reverted as well.