The project tiles and project grid / list view in the New User Experience (UX) do not come back with the same results from an exact same filter. The results in the Classic Project List view are a match for what is shown in Project Tiles.
Example: Project Titles shows 8 projects, while the Project Grid/List shows 12 projects.
This is due to the projects being checked as templates. The project tiles page filters outs templates. The Classic Project list filters out templates by default as well.
Release : All Supported
Component : CA PPM SAAS PROJECT MANAGEMENT
To check if this is the cause of the issue, you can add the Template field to the project grid column view in the Modern UX to validate if those missing from the tiles page have "Template" checked. From this view, you can also uncheck any projects that should not be templates.
If these projects aren’t supposed to be templates, here’s one cause that can make them templates: Projects created from a template are also templates.