In GENERAL a "release of all claims" does NOT restrict the ability to collect UI, it restricts the ability to sue, to claim that you were owed money or anything else by the company (although in CA, you can still go after the company for unpaid wages even after signing a release), including discrimination and wrongful termination claims.
In CA, where I am, I have never encountered a release that covers UI, as they violate state law and the companies I have worked for have usually had someone in them (I am in HR) who knows this and the clause never even makes it into the release. Generally the company is not able to make you sign away your ability to collect UI. UI is a state and federal program, as such contracts between employees and employers who are not the federal or state government, are not able to "sign away" rights that are state and federal. (This is why you can usually still collect on unpaid wages, as mentioned above, because those wages are governed by federal law and as such the company can not take away your rights under federal wage and hour laws)
Hard to give concrete advice without seeing the actual document.
1. Does it state anywhere that it covers UI?
2. Did anyone at the employer specifically mention UI?
3. If they are attempting to include the UI, are there any outstanding claims you could have against the employer? If so, you may be able to negotiate them removing the clause. Granted, you could likely sign and still receive UI (again depending on the state) but getting them to remove the clause makes it that much easier.
4. You may want to call and speak to a UI rep in your state...they may be able to answer you more specifically.
A few links you may find helpful....
Release of Claims - What Is a Release of Claims or Employment Separation Agreement
California Severance Pay, Separation, Release Agreements, CA Attorney