sdmax2018 is a bitcointalk username not a telegram username.
You are reading too fast.
and the post you quoted above shows that the user is telling him about a telegram pm he/she sent.
What I'm saying is that the connection would be clearer if the @sdmax2018 bitcointalk account also mentioned @sande123 as his telegram contact.
Is Andruu the only admin on that bounty group? If so, I guess that should be enough to conclude that they are one and the same person.
Sorry for reading your post wrongly.
Andruu is the only admin in the group and here is a thread where he mentioned his username and his bounty group in the telegram campaign part