This is just some DM with no logistic (real logistics, not target) experience floating some pipe dream. This will never, ever, ever happen. It will also never be a company wide directive. Let me tell you why.
Every store has a uniquely sized backroom and layout - Store footprint has zero to do with store volume. I have set up backrooms for AAA volume stores that are small footprint, and use an offsite storage, and I have set up backrooms for c and d volume stores with massive footprints. The real estate available is what you work with. As your inbound inventory flexes, so does your space.
You can't predict inbound freight flow - Inbound flow is functionally unpredictable. You get a piece count, and sure you can pull a dci, but functionally you generally have no idea what is coming, or in what quantity, until the day before. Trying to smash your stockroom to what essentially equals half of it's current size is only going to result in chaos.
Paying for stockroom footprint but not using it is a massive waste of dollars - Paying for an open stockroom with 20 foot aisles, but only using 6 feet of them is a huge waste of money. You have to heat/cool/light/clean the space. It would be far more cost effective to simply use half the stockroom and seal off/cut power to the other half. Low is not inherently productive. Ladders are not inefficient. Steps are inefficient. I ran multiple stockrooms and satellite warehouses packed to the brim with product. If you have sound logistic leadership to set up a plan for your stock, steps are minimized anyway (example: I set up a top sku aisle in my stockroom, top 5 skus from each dept were backstocked in that aisle. CAF pulls during mid day or slow periods pretty much always consisted of pulling mostly in that one aisle, instead of walking all over the stockroom for 20 items).
I don't comment much anymore, I'm some years removed from Target (and retail), but things like this infuriate me, because it's clearly not just non-feasable, it's also counter-intuitive to the entire point of the stockroom. Any time anyone fed me the "low and productive" line, I wanted to staple a post-it to their forehead that said "Moron". It's a reguritated bullshit Target term, made up by people who have absolutely no real logistical experience so that they can sound smart.
Edit: Before someone asks how, I changed the fillgroups of the top5 item skus by manipulating the items in UPC Maint on the S&L PC. I don't know if this is possible anymore.