Edit: This comment was written when the original comment was just "Would it hurt them to use ${x} instead of \{x}?"

This is covered in the article under "Alternatives", in the section beginning with:

> For embedded expressions in string templates, we considered adopting the ${...} syntax from the Java EE Expression Language (EL) rather than \{...}. However, this would force developers to escape every $ sign in the literal text of a string template while continuing to write $ without escapes in string literals and text blocks. This inconsistency could all too easily lead to errors.

...

> With the syntax we have chosen, frameworks can ease migration by providing a template processor that understands EL syntax. Developers can continue using ${...} while also having access to the Java environment via \{...}: