Should prosecutors be looking for and excluding Ch 55 expunctions petitions for violations of the ABC 106 by individuals under 21, since ABC 106 has a specific provision for an expunction process and probation or deferral of any kind is considered a conviction. Also the intent of the law was to track alcohol violations by minor offenders until age 21 at which time if they only received one violation under ABC 106 they would be entilted to an expunctions. Or is Ch. 55 just the catch all for expunctions?

Ch. 55 is the catch-all and applies broadly. There are a few specialized provisions for other expunctions, such as under the ABC or Ch.45. But I don't see anything in the language of those statutes or Ch.55 that prevents a person from applying for a Ch.55 expunction if they qualify for it, even if they might also qualify under another statute as well. (Practically speaking, you shouldn't apply for a Ch.55 expunction if you qualify under another section, since those are much cheaper and easier to get! But a lot of people aren't familiar with the non-Ch.55 expunctions and so just apply based on what they know.)

And while yes, it definitely prevents being able to track violations over time, that unfortunately is the purpose of expunctions. No real way around that.