It is common sense to assume racing greater distances will require an increase in running volume. But you do not know absolutely what amount of running mileage is required for her to be successful now, or in the future, at the 5k, regardless of what other athletes run. Lydiard thought even 800m runners should run 100miles/wk, but we know from the experience of successful athletes that is absolutely not required.
What we do know is that her current training has successfully helped her be the fastest 5000m collegiate woman in the history of the NCAA. She has been gracious enough to share an amazing amount of detail in her training to the media. That knowledge helped Elizabeth Leachman become the Foot Locker Champion. The old adage, “if it ain’t broke, don’t fix it”, probably applies here.
I don’t think any rational person would conclude she wants to run the steeple because there is less injury risk; the steeplechase carries greater inherent injury risk than normal track distance events.
Thus, we don’t know her motivation for wanting to run the steeple, but I assume her motivation (if it still exists) to want to try it, is to see if she can be successful at it.
There is no reason to think running the steeple will require more running volume. It will require a lot of additional technical and strength training not typically required for normal track races, and may require more overall training time than required for the 5k.
I brought it’s shorter distance as possible motivation, because from past interviews, she has said thinking about the diminishing time remaining in the race helps her get through the tough going. But that is a pretty common mantra with many runners.
Another appeal of a shorter race, like the 1500m, was mentioned by Cranny because of more ‘engagement’ in the race distance, particularly at the more competitive International level.