It is not a question of sematics

The relativity of of space / time is a fact that it is explained by the theory of special reativity

Let's see the following examples

Bilions muons pass through our body every seconds

Muons are generated by the collision of cosmic rays with the atmosphere
You can generate muons also in lab and you can measure their decay time

If you multiply the decay time x the speed of light you get some hundreds meters

How can the muons reach us , the atmosphere being some km depth ?

The explanation is given by the theory of special relativity

muons travels at a speed close to the speed of light
If you multiply the muon decay time by the cofficient of time dilation than you find out that the muon can cross the atmosphere

We can therfore state that the speed by itself slow down the decay process
For the same reason it is reasonable to assume that the speed slow down also the aging process of the twin pilot

This is however valid only for us , living in the earth spatial/temporal dimension

From the muon viewpoint the decay time remains constant but the atmosphere is only some hundreds meter thick

It is the time / space symmetry

P.S.

Just to clear up
The key concept is the so called :

Time / space interval

Common sense assume that space and time are unrelated measures

The theory of special relativity on the contrary demostrate that all the observers share the same " space / time interval" which is a combinattion of local time and local space

The twin of the earth "consumes", so to speak, only "time"
The twin on the srarcraft "consumes" both time and space thus his time consuption is lower ,the "space/time interval " being a constant for both twins

Useless to say that a/m explanation is non intuitive but it is confirmed by the experience :

a) Spatial missions
b) decay time of particle in particle accelerators
c) Behviour of particles coming from the space
d) Spectrum of far stars