I feel like warp corruption is a matter of when, not if.
First, let's assert this as a given.
Look vs. perceive.
Perceive: The Mechanicus renders data from its warp sensors in an abstract fashion. Perhaps Warp Energy or patterns is rendered as digitized swathes of color, series of numbers, pictograms. It mediates the experience of the Warp in to a data-driven display. There is much it doesn't display, or it breaks down that display into smaller, more manageable bits. (Think of vision modes or filters.) In the example of Harpies, they might show as an outline of light or a threat vector number value. I believe this is already somewhat standard technology on starships. They need to be able to communicate information about Warp energy to the crew, even if it's in its most rudimentary form. (Whether there is Warp energy or not, how much warp energy. Typically used by sensors and augurs to know when ships are translating from the Warp.)
Look: The Mechanicus tries to render as much information as it can from the Warp. Rather than creating an abstract representation of Warp data, it tries to include as much as possible as specifically as possible. So Warp Energy would be a background bloom of color, and the Machine Spirit would try to capture as true a rendition of a Warp Entity as it could against that background. Rendering swathes of emotion as changing equations. Layers upon layers of data, where each data layer interacts with the others, eventually leading to sensory overload. There's less filtering of information. In the case of Harpies, the Machine Spirit might try to render its actual shape, or the hellish light emanating from its eyes, and how the different metrics of Warp energy relate, react to and change based on it.
Obviously both still lead to corruption, both of the viewer and the technology. The better the detail, the more rapid the corruption.