Very often foundations and private organizations have rules that are difficult to understand. You should always go to them with your questions. They will not be offended or tie the question to your application. You are likely not the only one with these questions. Application guides, FAQs, and even webinars are very common for foundations and should always be sought out before contacting a sponsor.
Even federal programs have rolling deadlines. Typically this is tied to how their budgets function. If they receive an incredible proposal, they want to fund it as early as possible into their budget period in order to make sure they expend the funds. If they wait too long into their budget year and no proposal feels worth funding, they may not be able to use the money. If the foundation receives this budget from another entity, they may have to send the money back to the main institution--it doesn't roll over to the next budget period.
You can ask them general questions, such as how many proposals they typically receive in a calendar year and if they convene review panels on a regular basis or as needed. My hunch is that they are prioritizing funding any proposal that scores high enough, not necessarily the best project within a given year (perhaps you should ask if "year" = calendar year or if they have a different fiscal year). In the event that they get multiple entries though, they would surely fund the best project. Focus your questions such that you can learn about the intent of the program. Rather than asking bluntly "why are you doing it this way", the questions should focus on how the competition for this award is framed, because that is what you are trying to consider--what your competition looks like and who the reviewers are.
Depending on the foundation, scientists may not even be the primary reviewers of the work--board members may make the first call based on what they are interested in. Some foundations do not restrict topics, and so a proposal on robotics may be up against a proposal on climate change. If the board is more interested in climate change, they may opt for this proposal and ask for a scientific review to ensure the project is sound. These types of structures are more common when the proposal/research summary is very short (1-2 pages). Some faculty refer to them as "beauty prizes" because the academic rigor is not as intense, and sometimes the goal of the program is just to give money to science and attach the foundation to prominent scientists.
