If that were true, then attenuation would change instead of being fixed. Attenuation only changes when the equipment is changed or the modulation changes.
You're not so far off.
The first sentence above is correct - the attenuation DOES change.
The second sentence is wrong though. The fact that you believe it's true probably means that (a) you are lucky enough to have a relatively low attenuation figure, and (b) that your router rounds the reported attenuation to the nearest dB (like mine). Some report values rounded to the nearest tenth of a dB...
You said in an earlier post: "The attenuation is a function of the line length and the frequency it's measured at". This was absolutely correct. The bit that you are missing and which billford attempted (semi-patiently

) to explain is that the frequencies IN USE can change (subtly) with every resync. On my line (atten > 50dB, ouch) I can see varying speeds AND varying attenuations. It's always in the range 50-52dB though.
I think all of this stuff is explained on the kitz site (or links from it) but it's been a while since I read it.