"Unlimited traffic" with a surprise

I saw the service “unlimited traffic” on the FirstVDS website. Like, connect it, and have no problems. Of course, with reservation :

Please note that we reserve the right to deny the service “Unlimited traffic” if it is used to generate “parasitic traffic”: equalization of ratios from other providers, DDOS attacks in any direction, torrent clients, etc.

Of course, neither the alignment of the traffic nor the torrents I planned. And even more so, to use for DDoS-attacks "in any direction."
')
The wording "DDoS-attacks in any direction" caused me suspicion. As it turned out, not in vain. I wrote a letter to sales@firstvds.ru:

Hello, gentlemen.

I saw you have the service "unlimited traffic" - a question immediately arose.
If I buy VDS with this service, and I get DDoS and generate a couple
hundreds of gigabytes of incoming traffic, this traffic will not be for me
cost extra money?

And the answer came to me:

Hello, Alexey.

This is stated on the website:
firstvds.ru/en/technology/faq/servicesvds.html#unlim .
Add: if we notice that the user is flooding, then
he will definitely pay for “parasitic traffic” in this service
in the future, the user will be denied.

This is how it is. Then I wrote the second letter:

Hello Tatiana.

TA> About this site says:
TA> firstvds.ru/en/technology/faq/servicesvds.html#unlim .

It says: “We draw your attention that we reserve
the right to refuse the service "Unlimited traffic", if it is used
to generate “spurious traffic”.

I couldn’t even imagine that if a client is attacked, then this
it turns out he uses traffic to attack himself.

TA> I will add: if we notice that the user is flooding,
TA> he will definitely pay for "parasitic traffic" in this service
TA> in the future the user will be denied.

Those. if the client generates 10-20 terabytes of non-parasitic
traffic, everything is OK, and if it is 100 gigabytes due to the fact
that someone is attacking him - he gets on the money with your company?

What is the fundamental difference between 1 gigabyte of normal traffic
and 1 gigabyte of traffic that heats up to the client due to the attack?

No answer has yet been given.

Update: on the 23rd, after almost three days (if sales are so slow, then what’s going on with support?) The answer came: “These are our terms of service. They are not discussed. " Bravo.