While Sun Qiang was not a master teacher, having spent a long period of time with Zhang Xuan, he was still aware of most of the rules concerning master teachers.
Their Old Master, Yang Xuan, was one of the top experts of the continent, but even the strongest of experts would have their own weaknesses that others could exploit. In order to prevent the Otherworldly Demonic Tribe from designing a trap to deal with them, the appearance, strength, cultivation techniques, battle techniques, and other private information of those experts were made classified secrets that only the top echelon of the Master Teacher Pavilion was privy to.
Yet, an old fogey who came out of nowhere actually had the cheek to ask him for those details! Was he unaware of the rules?
"You are asking if I am worthy?" Yang Xuan could not help but chuckle softly upon hearing those words.
I know a lot of you might detest Sun Qiang as a character, but one of the avid Sun Qiang supporter on the Discord channel whom I'll address as Tr*be-san has made a fair point about him that I'd like to share here.
It might appear that Sun Qiang is arrogant and a show-off, often causing much trouble for Zhang Xuan, but his actions are actually well-calculated and rational if you think about it from his point of view. The only reason why it felt cringeworthy to us is because we know that 'Yang Xuan' is a fake identity that Zhang Xuan had made up, but Sun Qiang doesn't know that.
Sun Qiang knows how to make use of 'Yang Xuan's' identity to pull his weight and get things done (such that obtaining pinnacle spirit stones for Zhang Xuan through exploiting 'Yang Xuan's' identity a while back).
On top of that, if we pay careful attention, he had only exploited his identity in scenarios where he's confident that it'll work out well, such as in front of master teachers or in cases where 'Yang Xuan' has already established his seniority over the other party.
In other words, while he did act incorrigibly arrogant, he knew for certain that he would be able to get away with it (under the assumption that 'Yang Xuan' is real, of course), and he also thought that it would be inappropriate for him to behave too humbly before others when he's 'Yang Xuan's' butler, which is why he behaved the way he did.
What really went wrong in Sun Qiang's case was that he had received wrong information regarding 'Yang Xuan', which led him to estimate his own standing wrongly, thus leading to the series of tragedies. This could be seen in how Sun Qiang did lie low when they first entered the Sanctum of Sages, not daring to cause any trouble even when he was snubbed by others. It was only when he learned of Yang Xuan's standing in the world did he exploit it in order to raise his and Zhang Xuan's standing in the Sanctum of Sages, and that did bring quite some benefits to Zhang Xuan too (like Zhan shi personally bringing him into the Inner Sanctum, so on and so forth).
I hope that this alternative point of view could allow you to appreciate Sun Qiang a little better in the novel. Things did go wrong for him, but he's definitely no reckless fool.