I think the there is also a difference between objection and reservation besides severity. I think reservation is used in the legal sense, from my basic understanding
A reservation is like an individual opt out of a specific provision, while allowing the resolution to pass, while objection would not allow the resolution to pass.
For example: India can have reservations about a provision on assisting counter terrorism in Afghanistan, while the motion passes. While India can also object to the ascendance of Cambodia in SCO as a full member.
Also many Chinese scholars already mentioned the veto problem in SCO, I think we should trust their judgement.
Some non Chinese sources: