You can have a unique style at any level of a design career - even as a hobbyist. Many do inherently. But one also needs the ability to show off your style in any portfolio if employment is the goal.
There are a couple tell-tale lines from your question....
Both projects are brand designs
If your portfolio does indeed only include two projects, and both of them are focused on brand identity, you are not giving a potential employer anything to judge. Anyone can get lucky and create two decent brands over a period of months, if not years. That does not mean they can work efficiently, effectively or create a broader range of projects.
The other line....
don’t you have more projects? We need to see more, to rank/understand your graphic style
To me, it's clear the employer really needed to see how you would handle projects other than brand identity projects. Anyone applying for an entry level position as a designer is going to be called upon to probably create a wide range of projects. Entry level designers don't get to work on the brand projects. They get the grunt labor stuff the senior designers don't want to work on. Senior designers keep things like brand projects for themselves. However, brand projects are more rare than some may think. If there are no senior designers, then sure you may get a brand project every once in a while.... but again, they are typically far, far, far, more rare than everything else which needs to be done.
The bulk of any work for a new designer is often in collateral materials - you know they less exciting stuff - fliers, posters, advertising, web banners, etc. By focusing only on brand identity, there's no way to know how you would handle projects with much, much, more text, or using mandatory specified photos, or calls to action. There's no sense of how well you can edit photos or create unique artwork for a specific collateral items. There's myriad things you can't tell by merely looking at 2 brand projects, even if they are stunning brand designs.
The portfolio of a designer just starting out should never be targeted to only one area of design, such as only brand identity, unless the employer has specifically stated they are only interested in brand design. Most often if you are using a physical portfolio, you want it to have at least 8-10 pieces and each one of those pieces should be a different kind of project in order to show a range of skills if that's at all possible. Obviously on the web you can show more if you have more.
From the sound of your question it would appear that you really didn't give the employer anything to judge your ability to be diverse and effective with a range of projects. Project diversity is very important in a young designer's portfolio.
I don't think they were asking for a "unique style", rather they were asking to see how you'd design things other than brands.
