We're trying to reach ML2. But we have to deal with both large projects (from 700h to 10,000h) and small projects (<>700h)
When we conduct a SCAMPI A Appraisal we "sample" the projects that an organization is executing. Even though we may only look at a subset of projects, the expectation is that ALL projects within an organizational unit are performing at ML2 (or 3, 4, or 5). So that imprecise answer is no, you must be performing all of the practices on all projects.
The more precise answer is that there is room for "alternative" practices. If you have, say, a one-person project, there should be alternatives to the standard process which is probably designed for teams of programmers. An example may be practices that require progress reviews. You may require larger teams to have weekly team meetings that are just for the project team. In a one-person team, that person is having that same meeting 24x7! So a practice like that may not be relevant as an event and may not be represented by evidence.
Now, the GOAL must be achieved - even if an alternative to the practice is performed. So you just can't do NOTHING, but there is some flexibility in the performing alternates to the practices.
Whether or not your Lead Appraiser understands these alternatives is another story though!