I have doubts because I haven't seen this in the list of criticisms that Aurangzeb usually receives in numerous articles, and because I have myself seen several entries on religiously sensitive articles on Wikipedia to be based on extremely late and propagandist accounts (especially about medieval history where the quality of Wikipedia articles is highly questionable). Additionally, sawing people in half is not a punishment that I have heard of being administered in this period in this part of the world at all.
There was no written record of that incident when it happened. The Hindu states:
For the historians, difficulties have been created because the execution of Guru Tegh Bahadur in Delhi in 1675 is not mentioned in any of the contemporary Persian sources. Nor are there any Sikh contemporary accounts,
The wikipedia page cited by OP (the page was updated after OP cited it. The version OP cited is this) is based entirely on a single reference which is also based on another single reference. Its reliability is questionable. The updated version of the same wikipedia page states,
According to various oral accounts, Mati Das was executed on the order of Mughal emparor Aurangzeb. Traditional Sikh sources state that he was executed because he refused to convert to Islam. But there are no wrriten account of his execution. Mughal empire records from 17th century explain his death as punishment for challenging the authority.
You are not telling the whole story here. Mati Das was not executed in isolation, but as part of campaign against the 9th Sikh Guru, Tegh Bahadur. Aurangzeb had arrested Tegh Bahadur and tried to get him to renounce his beliefs by torturing him for weeks. When that didn't work, Aurangzeb tried to convince him by executing his close friends and disciples. He imprisoned Tegh Bahadur in a cage and then executed his friends while he watched. The executioners devised the most cruel ways to execute the disciples, of whom Mati Das was one, in order to try to persuade Tegh Bahadur to recant. For example, another one of the disciples was boiled alive.
The method of sawing a condemned in half is very old. The victim is tightly fastened between boards lengthwise, like a sandwich, then the boards are sawn in half.