+1 with TBS's opinion. No matter what size blade, which grind, which steel, I find my hanging strop gives the best results.

I have a small sprung paddle strop which I use for travelling. It's ideal because it's shorter, more compact, and won't suffer from being squashed or bent out of shape when put in the suitcase. BUT, I find I have to double my number of passes on it to achieve the same results. (Makes sense, given it's a lot shorter than my hanging strop!)

Do TI make sprung strops? Dovo do, and so it wouldn't surprise me if the recommendation for a sprung strop is just a little marketing to get repeat customers.