Will using Slow negatively affect my score?

While playing Touhou: the Embodiment of Scarlet Devil, I noticed in the summary statistics of a play that the game keeps track of your overall Slow percentage. I've found that using Slow definitely helps me with fine tuning my movement when fighting bosses, so I'm trying to force myself to use it more often to help me get through tough battles (my tendency to forget to use my bombs is another matter entirely).

However, is this detrimental to how the game calculates my score? Is using Slow a bad habit to form?

Holding shift for focused movement does not affect your score.

The "Slowdown rate" percentage on the score page shows how often the game slowed down (e.g. due to a slow computer), rather than the amount of time spent holding shift. It's mentioned for comparison to other players' high scores, because a high slowdown would give the player an advantage.