Note that the article you quote also says
En caso de que el alzamiento fuera armado o si se produce “combate entre la fuerza de su mando y los sectores leales a la autoridad legítima, o la rebelión hubiese causado estragos en propiedades de titularidad pública o privada, cortado las comunicaciones telegráficas, telefónicas, por ondas, ferroviarias o de otra clase, ejercido violencias graves contra las personas”, las penas se elevan hasta los 30 años de prisión.
My translation1 for the benefit of third parties:
If the uprising is armed or results in "combat between the force under his/her command and those loyal to the legitimate authority, or the rebellion should have caused damage to publicly or privately owned property, cut communication (whether telegraphic, telephonic, by waves, railways, or of any other kind), or exercised serious violence against persons", the penalty increases to up to 30 years' imprisonment.
The key phrases I want to highlight are "If the uprising is armed or ... exercised serious violence against persons". Implicitly, sufficient "violence" for the charge of rebellion can occur without the use of arms or infliction of serious injury. Since the prosecutor will consider events of the past few months as a whole, and as relevant context where not directly included in the charges, the bruises and bites sustained by some police officers on the 1st of October can be adduced as both violence and relevant.
El escrito dedica numerosas páginas a relatar, colegio por colegio, los principales incidentes registrados durante la jornada de la consulta ilegal. Maza responsabiliza a Puigdemont, Forcadell y el resto de querellados de estos altercados: “Los momentos de violencia vividos en gran parte de los centros destinados a llevar a cabo la ilícita votación fueron el resultado de la pertinaz actitud de los querellados de celebrar a toda costa el inconstitucional referéndum imponiéndolo por la fuerza de los hechos consumados y de la multitud movilizada”.
Source and my translation:
The document dedicates numerous pages to recounting, polling station by polling station, the main incidents recorded on the day of the illegal consultation. [The prosecutor] Maza holds Puigdemont, Forcadell and the other defendants responsible: "the moments of violence experienced in a large proportion of the centres selected to carry out the illegal vote were the result of the persistent attitude of the defendants to hold the unconstitutional referendum at any cost, imposing it by the force of fait accompli and the mobilised masses"
It seems that he might also be aiming for the 30 year penalty on the basis that it was armed rebellion, because he also speaks about
la asunción en exclusiva del mando sobre los Mossos d’Esquadra, cuerpo policial integrado por más de 17.000 efectivos armados, con el potencial efecto intimidatorio que los mismos representan para quienes intenten hacer efectiva la vigencia de la Constitución
The assumption of exclusive command over the Mossos d'Esquadra, a police force consisting of more than 17000 armed people, with the potential intimidatory effect which they represent to those who might try to uphold the Constitution
I note as a secondary point that El País reported last week that the intention was to lay charges of sedition/rebellion, leaving the judges to decide which was the correct charge, because rebellion is outside the jurisdiction of the Tribunal Supremo de Justicia de Cataluña, and so by including it in the charge sheet they could bypass the aforamiento of the senior politicians involved and bring the case before the Audiencia Nacional instead of before the TSJC. Unfortunately I can't find the right combination of search keywords to dig out the article: if anyone else can, please edit in a link.
1 NB "persons" is idiomatic English in a legal context, but not otherwise.