Because the "conversion" lovecraft offers isnt really a true wvo conversion. All they do is add a big heated filter inline to the stock setup. The engine starts on cold wvo which causes coking of the injectors and polymerization in the cylinder walls that will later on ruin the engine.
Trust me im not against wvo conversions but i do know what can go wrong with single tank "conversions"
Here is an example of a coked injector. I pulled 5 of them from my ex-300SD when i was experimenting with wvo/diesel/rug mixes.
Bottom line. Get a 2-tank kit.
There are many affordable 2-tank kits. IMO greasecar with a vegtherm added is about the best option in terms of efficiency and price.