Married sectors are for availability - not for fares

With married sector availability, it may be possible that A-B has I class available and B-C has I class available but A-C via B does not have availability

For the fares , for A-C via B , travelling part way in ecomony and part way in business would not be any cheaper than business the whole way

If someone has LGW-DXB-BKK, it would need to change the booking to LGW-DXB and DXB-BKK as 2 separate fares to have them in different classes. If on a through fare., the whole journey will be charged as a business class fare

You be patronising, but I do know what married sector logic is

from IATA glossary

Married segments is a term used to identify two or more segments in an itinerary which are actioned as a single unit (set). Acceptance and sending of marriage information is controlled by bilateral agreements. See IATA Recommended Practice 1777 and 1777a.