I am very skilled in cursive handwriting, and I can tell you that such skill has little to no effect in forging another person's signature. Most often, people forget how cursive really works and just memorize a fast signature. This makes scrawled messes like you can usually find on a doctor's note common, and any real ability in cursive only makes you more aware of how much of a monstrosity it is. While cursive may make your hand steadier, forging a signature requires skill in the area of being able to draw and copy very well, not the skill of cursive. Of course, if you're interested in getting a perfect forgery it is much easier to use conveniences of the age such as cameras.
As for how it relates to information security, a signature is another imperfect verification process meant to slow scammers. It is possible to forge a signature, either with a skilled hand or with digital tools. However, if some scammer makes a fake card with your credentials, they likely will not know or care what your signature is. When you detect the malicious activity on your account, it is easy for the bank to check your signatures to find the fake ones. Your signature will also be checked on any large check. However, when you're buying five dollars worth of groceries it will likely be stored for a little while and never seen again. Any real understanding of cursive is pretty meaningless to this process.