No, There is no imperative to create a new construct here.
When a metaphor ''loses its metaphorical properties'' due to the demise of colloquial meaning of its components, where the meaning remains we call this an idiom. Where the meaning is lost entirely, we call it a dead metaphor. Both of these descriptions are accurate, depending on the time, place and persons from and to which the phrase is spoken or written.
Also I believe the following phrasing manipulates the outcome of the discussion:
'high point [e.g., of a career]'
The above definition includes his very own implied assumption of "high" being strong or successful! It would be far more accurate to simply use the following phrasing in our definition of the zenith of a career:
'strongest or most successful point [e.g., of a career]'
I believe this is simply a discussion of the difference between metaphor and idiom.
In the case of the phrase "Falling in Love" we're really looking at an idiom. Whether or not a person understands this phrase is a combination of 1) whether they've heard that particular idiom, and 2) whether idiom exists in their native paradigm at all (e.g. certain languages have no idioms, and the concept of idiom can be a challenging new one).
However, this is completely separate from the fact that a limber mind can interpret meaning in places where it has not been literally defined. We call this metaphor.
Consider backfire, backlash, kickback, and payback.
backfire: a miscalculation that recoils on its maker
backlash: a strong negative reaction, as to some social or political change
kickback: a sharp violent reaction
payback: a bad or unpleasant thing that someone does to you after you've done something bad or unpleasant to them. E.g. payback on French Nazi collaborators after WW2.
Best Answer
A local New Zealand term. Imagine a tank holding liquid. The level of the liquid represents the numbers of employees of the company. The tank might have a slight leak at the bottom, so the liquid level very slowly goes down. Or some might evaporate. That represents the slow loss of employees through resignation, death, retirement, etc. Now imagine a lid floating on the liquid. That prevents you removing liquid with a ladle, cup, or siphon. The lid represents the policy of not reducing the staff by redundancy or dismissal. As the water level sinks (goes down) so does the floating lid. The gradual loss is sometimes called 'natural wastage'.
The term 'sinking lid' is used in New Zealand more generally about policies where the level of something is allowed to reduce naturally, rather than by intervention. For example, the Wellington city council has a 'sinking lid' policy regarding licencing of poker type gambling machines in pubs and clubs. No new licences (British spelling) are granted. They call these devices 'pokie machines', I see in the Stuff (NZ) web site
A related term is 'cap'. If you put a cap on something (wages, bus fares, number of employees, whatever) you prevent that level or amount from rising above a selected limit.