The issue is definitely the £100k cliff edge and if you havent already got on the housing ladder.
We bought around 10yrs ago, a 3bed house in a rather undesirable part of south London for around £350k. Mortgage currently around £1500. Plus we have two DC in childcare - one with 30hrs funding and one with 15hrs funding. Total childcare bill £1900.
We have a joint income of £120k between DH (FT) and me (PT) - was probably more like £150k when i was FT. We have a comfortable life and appreciate how lucky we are.
But if I was a single earner of £100k, my take home pay would be around £5.5k and I would lose all my childcare benefits.
To buy our house today, you'd be looking at a mortgage of £2.2k+, plus once you lose TFC and funded hours, nursery bill would be around £3k min, maybe even higher. So thats already your entire salary before we even get into bills, food, necessary spends etc.
It does seem very unfair to me.
Back to the article and "Henry" should probably give up his flat and find a houseshare to be able to save a deposit for a flat rather than paying so much in private rentals. And probably reassess which part of London he lives in (like we had to.) But its understandable why someone in their mid 30s doesnt want to houseshare anymore. In the end, he cant have it all though so he would need to decide whats more important.