Not in my experience, to have a link flagged or ghosted you would need to seriously be spamming it with a really high frequency over a short span of time.
There are countless Pinterest accounts out there who only post there own URL's consistently, Look at accounts like Buzzfeed all the way down to those accounts about Blogging Mom's making money from home. They all solely post their own links over and over and if anything are rewarded for this because of one simple fact. Repins.
By spacing the Pin's out mixed with all kinds of other pins and links especially on a Business Account you are doing what every other Marketer / Blog / Product or Service are doing on Pinterest and this is what they want, otherwise why would they be flaunting the Improvements to the ad platform to offer you further capability for exposure and clicks to your domain linked Pins?
The power is not so much in how many pins you post with your URL's which is where your focus seems to be (As the amount needed to rank could really vary per Niche / Keyword), but more but the frequency in which you are repinned by users (Or your own accounts) that find you pins valuable on the group boards you are posting to, this is where the ranking really starts to show.
By consistently re-posting the same pin your are essentially stacking the social engagement which is where the ranking starts to show. Again this is where you see multiple pins ranking for the same keywords in search as
@William702 mentioned as you slowly begin to stack social engagement so high you dominate that Niche / Keyword and all the sub keywords that tail off from that.
Example: You rank #1 for "black leggings outfit" you probably then rank high for "black leggings outfit winter" also which you can have multiple pins ranking for to with different images and URL's.
You can actually check that example by searching keywords, then add a suggested long-tail's and you will see the same pins from the same URL's and accounts ranking highly against others solely going after the long version of the keyword. So you are not only ranking for 1 Keyword but multiple variants of that once you've stacked the amount of engagement and repins.
This could not be achieved simply by Pinning your images and URL's with only one account over and over hoping to rank with little to no repins from other users, the algorithm for ranking is looking to total up all the repins, comments, tried, shares externally to position you in search. This simply would not be possible if one account was the sole Pinner / Repinner of that URL or Pin, you are heavily reliant on the engagement of others and having this spread across Pinterest.
