Why would you recommend OSWE? What's an example of a specific benefit you'd get in appsec (also my specialization!) by holding that certification?
You can find the syllabus here: https://www.offensive-security.com/awae-oswe/
Something that is really interesting I think is the whitebox approach that some people in infosec might be missing if they don't come from a developer background and never botherered looking at the code introducing the vulnerabilities.
If you want to learn appsec I recommend Web Security Academy: https://portswigger.net/web-security
Just that I would recommend it because I felt good going through the challenges and that someone took the time to set up VMs and writeups for me.
In conclusion, it was more of a consumption thing than an investment.