The judges looked for any evidence in secondary sources of whether parliament intended to amend the definition of woman from that of the Sex Discrimination Act that the EA was replacing, and said they couldn’t find any indication that this was the case.
Honestly, it doesn’t really matter what the civil service drafter of the statute thinks the purpose of the law was originally supposed to be - parliament still reviewed each revision and ultimately signed off on the wording used, so even if someone did once suggest saying “pregnant person” or whatever during one iteration, that’s not the version that was approved by parliament and passed into law, so it’s obviously not what Parliament wanted the law to say.
Furthermore, I would say the fact parliament actively considered changing ‘woman’ to ‘person’ in respect of female biological functions, but then ultimately changed it back to ‘woman’ gives even more weight to the notion that they intended woman to mean biological woman.