I've not spent too long thinking on the following, so I'm prepared for someone to say I'm totally wrong, but:
I feel like the services economy can be broadly broken down into: pleasure, progress and chores. Pleasure being poetry/literature, movies, hospitality, etc; progress being the examples you gave like science/engineering, mathematics; and chore being things humans need to coordinate or satisfy an obligation (accountants, lawyers, salesmen).
In this case, if we assume AI can deal with things not in the grey zone, then it can deal with 'progress' and many 'chores', which are massive chunks of human output. There's not much grey zone to them. (Well, there is, but there are many correct solutions; equivalent pieces of code that are acceptable, multiple versions of a tax return, each claiming different deductions, that would fly by the IRS, etc)
AI progress depends not just on ideation speed, but on validation speed. And validation in some fields needs to pass through the physical world, which makes it expensive, slow, and rate limited. Hence I don't think AI can reach singularity. That would only be possible if validation was as easy to scale as ideation.
I agree with you on construction and physical work.