I am really confused! Why did Dan boost his Hurricane : when comparing it to Dignics on youtube?
Most people don't boost their rubbers. Rubbers are made to be played as-is with their own characteristics. When people want a faster and/or spinnier rubber, they usually buy a different rubber that's faster and/or spinnier. They might even keep the same rubbers and just use a faster or flexier blade.
The only commonly boosted rubbers are Chinese Tacky rubbers, like Hurricane 3. Most people, like me, play with it non-boosted, but some choose to boost them because Chinese Tacky rubbers are particular and have a very hard sponge. Boosting it makes the sponge less hard, and gives it more European/Japanese-style rubber qualities, mainly added speed and some added spin, but also less control. In his Dignics 09C review, Dan boosted Hurricane 3 in order to make it as similar and comparable to Dignics 09C as possible.
AK47's are Euro/Japanese-style Non-Tacky rubbers from a Chinese brand (Palio), so they already have a softer/faster porous sponge that is factory-tuned and doesn't need to be boosted. Unlike Chinese Tacky rubbers and their hard dense brick sponges, Euro-Japanese-style rubbers can suffer and damage more easily when booster is applied to them.
There you go!