TinyMCE Issues in Magento 2.3

Would an instance of SomeClass be without sharing?

Yes. Note from Using the with sharing, without sharing, and inherited sharing Keywords

Implementation Details About with sharing and without sharing Keywords

• The sharing setting of the class where the method is defined is applied, not of the class where the method is called. For example, if a method is defined in a class declared with with sharing is called by a class declared with without sharing, the method executes with sharing rules enforced.
• If a class isn’t declared as either with or without sharing, the current sharing rules remain in effect. Therefore, the class doesn’t enforce sharing rules except when it acquires sharing rules from another class. For example, if the class is called by another class that has sharing enforced, then sharing is enforced for the called class.
• Both inner classes and outer classes can be declared as with sharing. The sharing setting applies to all code contained in the class, including initialization code, constructors, and methods.
• Inner classes do not inherit the sharing setting from their container class.
• Classes inherit this setting from a parent class when one class extends or implements another.

Again, note:

Classes inherit this setting from a parent class when one class extends or implements another.

Get rid of the -l and use -1 instead. Really, it's all in the book.