I think someone commented that they just beefed up the supporting metal a bit.
Not a bit... a lot! On a 2013 such as yours, it's just a matter of removing a half dozen relatively flimsy brackets bolted on with maybe a couple dozen nuts and bolts, and both running boards will come off quite easily and with minimal hassle. They will leave behind a rocker trim with small cutouts where the brackets used to be, barely visible to the ***** eye. If those cutouts really bother you, down the road you could just buy a new pair of trim pieces to restore the original look. On a 2015MY or later, removing the factory side steps / side impact protection devices would be more involving (and technically illegal.) The bracket is indeed much beefier and heavier, and there are crumple pieces under the chassis as well.
Pretty sure you can find Ikea-like fitting instructions for the accessory side steps on your LR4 in Topix, if you want to "reverse engineer" their installation to take them off... Easy peasy. Try:
https://topix.landrover.jlrext.com/topix/content/document/view?id=114121&groupId=1660
Regarding the heated windshield missing on yours, bummer. On most recent models (including the new Disco, I am sure) Land Rover has made the non-heated screen a NCO on trims and packages where the heated windshield is included as standard equipment, or made it a self standing option altogether instead of a component of a pack. That's specifically to address complaints from owners who like other features of the cold weather pack (heated seats, mirrors, steering wheel, washer nozzles) but can't stand the sight of those filaments sandwiched in the windshield and/or happen to live in areas of the US where the heated windshield is kinda overkill anyway, such as Florida or here in So Cal... That was not yet the case on your LR4, though.