https://www.singaporeair.com/en_UK/s.../ne0822-221122
“Flights SQ52 and SQ51 that serve the Singapore-Manchester-Houston route will operate thrice weekly instead of four-times weekly from 28 March 2023.
SIA will launch a new twice-weekly service between Singapore and Manchester, SQ302 and SQ301, operated by the A350-900 long-haul aircraft, from 2 April 2023.”
So one flight a week is dropped for IAH, but two new flights a week added for MAN (that do not continue to IAH).