The purpose of this change in TextParser::parseDocument method is to catch TemplateProcessingException before fallback to generic Exception class in. TemplateProcessingException may contain line and column information in its fields, which is easy to access when handling parsing errors.

I stumbled upon this scenario, when building custom validator for end user defined templates in web based editor. In this case, it is important to have line and column where template has errors.
Currently, TextParser looses this information when catching generic Exception.

Currently, Thymeleaf contains 3 exception classes that maintain line and col information: TextParseException, RawParseException and TemplateProcessingException.
Another approach could be introducing custom exception class dedicated for containing line and col properties that could be inherited by those 3 mentioned above, but it would need bigger refactoring.