Yesterday I saw SWR working 2P50 https://www.realtimetrains.co.uk/service/gb-nr:L51843/2025-06-04 (forming the 1510 Haslemere to London Waterloo) on arrival at Waterloo. I was surprised to see a two digit former-Southern-Region-style headcode displaying on the matrix panels on the sides:

Apologies I wasn't able to do a better job with the reflection.
According to https://sremg.org.uk/headcodes/eheadcodes/eheadcodes01.html, 73 was (at least at one time) the headcode for "Waterloo - Portsmouth & Southsea (slow) via Worplesdon", which sort of fits. Unfortunately I was unable to see if the outbound working changed to a suitable headcode for a Portsmouth fast...
Is this new (with nationalisation?) or just something that SWR have always done and I've never noticed?

Apologies I wasn't able to do a better job with the reflection.
According to https://sremg.org.uk/headcodes/eheadcodes/eheadcodes01.html, 73 was (at least at one time) the headcode for "Waterloo - Portsmouth & Southsea (slow) via Worplesdon", which sort of fits. Unfortunately I was unable to see if the outbound working changed to a suitable headcode for a Portsmouth fast...
Is this new (with nationalisation?) or just something that SWR have always done and I've never noticed?