Explain build process relationship

Luet version:
0.32.5

When building a package that has build dependencies on other packages, if anyone of these packages change in the three luet will rebuild all packages from the changes package.

Let's say we have
pkg a to d

a is base layer
b is file and requires a
c is file and requires a
d requires b and c

if b is changed Luet will rebuild c, even if c is already built and has not changed
if c is changed Luet will rebuild c as it should.

So in cases where i have 15 different packages that is required to to build a single package, if i change anyone of those packages based on what order they are listed in the required section. Luet will rebuild all ascending packages. This causes unnecessary builds. Is this how luet is suppose to function?

The following repo can be used to test this
https://github.com/krise86/luet-test
make a, b c d
change b make d (will rebuild c)