You aren't taking what he said seriously. The junior could also get sick, present management issues, etc.
If this person plus a junior represented "1.3 engineering knots," he's saying... "actually, I'm still 1.3 engineering knots without him."
When this person leaves, they go find someone else who is 1.3 engineering knots. The junior represented .3, without the 1., it doesn't matter that much. Headcount strategy shifts.
If your company can treat people as cogs this way, your company has zero value add/domain knowledge. A company's value is what it value adds, what domain knowledge/expertise it has, or cheapest price. If all you have is cheapest price, you will lose over time. You will be undercut. You won't have the domain knowledge to adapt, to see future changes coming down the path.
So the company you talk about is already in the entropy vortex. It has no momentum. It has no future. It just hopes it can keep doing what it is doing now.
If this person plus a junior represented "1.3 engineering knots," he's saying... "actually, I'm still 1.3 engineering knots without him."
When this person leaves, they go find someone else who is 1.3 engineering knots. The junior represented .3, without the 1., it doesn't matter that much. Headcount strategy shifts.