First of all, I'd also like if this process has a proper name, I just named it the way I call it.
What I mean with 2-step installers is those installers that will make user download an (usually small) installer, then when user runs the installer, it downloads more content. For reference, think of most Google apps. For example I just downloaded Google Photos, which is a 1.1Mb file. Once you run that file, the real program is downloaded and installed.
While at first it looks nice to have the program you want to install downloaded in a few seconds, I think it's really frustrating to see that in fact you didn't download the program, but something else, and your real download is going to start AFTER that original download of the installer.
Thinking about the security side, if I gave permission to the installer as an admin, the newly downloaded stuff won't request for any additional permission, at least not with a normal configuration. I think this could be a HUGE security concern, but I'm not an expert on the subject, so really can't tell.
I know one of the most common reasons for this is to bundle unwanted software (SourceForge did this for some time, don't know now. Adobe Flash still does it, including McAfee unless you uncheck a box), but I know other software companies don't do it for this reason, yet they use the 2-step installer approach.
What's the rationale or purpose behind this? Are there any kind of technical, usability or security reasons for this?
EDIT: After installing Google Photos App on PC, now I see Google bundled unrequested software (specifically Google Docs, Google Sheets and Google Slides)