Whenever ETs abduct people by taking their bodies through solid structures, such as through walls and ceilings, is this a form of travel that is accomplished through manipulation of time?

Strictly speaking, this is not so. It is not time travel per se although there is some fluidity of time depending on the dimension one occupies. This is a complex phenomenon to describe, but you can see from known examples of people subjected to such manipulations that there is missing time involved with their experiences so it is not that they simply disappear and then reappear almost instantly, there is a time-lapse that is unexplained, if indeed there is conscious awareness something has happened but no details are recalled. That is the more common scenario—that people remember driving somewhere, walking in the woods, perhaps seeing something unusual in the sky and then wake up often hours later down the road or in a different location many times, and have no awareness of what took place in the interim.