What does this mean ? The denser the pips are for a pips out rubber, the more the ability to create both top-spins & back-spins. So when you reduce the pip density you reduce the ability to produce spin.
There seems to be a myth that this rule was targeted at Liu Guoliang but this may really not be true though Liu Guoliang himself had claimed that it affected him. Since Liu used smooth rubber on one side (for top spins) & short pips on the other side (not for top spins but as a variation from the smooth rubber side & I think his contrasting rubbers gave him the variations and not as much as his ability to produce top spins using short pips ).
But ITTF used this excuse (Liu Guoliang's success with pips) to further limit the back spin players (choppers) because lot of robotNazis complained to the ITTF that the 1998 Durban Aspect Ratio Reduction was not sufficient because they claimed that the reversal of the glue ban rendered the 1998 Aspect Ratio not that useful (which is far from true of course but when robotNazis say jump, ITTF does not ask Why but only ask How high). Also the robotNazis complained that the 2000 big ball was effecting THEIR ability to put more top spin because ITTF limited the glues.. Keep in mind that friictionless blocking style was not as prevalent in 2003 as is now. Also Dr.Neubauer changed pip design parameters other Aspect Ratio to create more deceptive long pips to retaliate against his business rival Scholer's passing of the 1998 Durban Aspect Ratio Massacre. But of course Scholer retaliated against the Dr.Neuba ... etaliation by passing the Frictionless Pips Ban in 2008
So the bottomline is that the ITTF's Pip Density Reduction Regulation of 2003 was primarily to further limit the choppers, but not even probably 100 players understand this. No documentation is even available from ITTF on how this was discussed & passed and the who voted for it & who voted against it.