For any parents starting to get worried: toe-walking is completely normal for many children below 5 years old and even older[1]. Usually they grow out of it as they get older. So I would definitely not consider that a sign pointing to the possibility of autism.
But it can be one flag (of many) pointing to a sensory processing disorder and should be noted if other behaviors are seen.
My son toe-walked. We did some mild sensory-processing screening and therapy which helped. It also turned out that his tendons were too short and he needed serial casting to get them stretched out far enough.
The study you linked appears to have one possible flaw. It reports on whether a child walked on their toes 'at some time'. In the many kids I've been around with autism, it's impossible not to notice the toe walking because it is so frequent. For our child, we would actually be more inclined to notice when she didn't toe walk.
If you combine this one with another couple symptoms, it's best to get it checked out.
Just to throw a anecdote on: I picked up toe-walking when I was a kid in response to regularly having to walk around barefoot on gross locker-room floors. In my case, I only do it when barefoot, and these days my heels are typically only about about an inch above the ground.
My son toe-walked. We did some mild sensory-processing screening and therapy which helped. It also turned out that his tendons were too short and he needed serial casting to get them stretched out far enough.