>C# and Java standard parsers
Not sure which parser you consider standard, as Java doesn't have one at all (in the standard libraries). Other than that the existing ones just take the target type (not json) when they deserialize into, e.g. int, long, etc.
That blog post treats Jackson as the de facto standard Java JSON parser/formatter which seems reasonable.
That's bit much - (unfortunately) the codebase uses at least 4 different json libraries (perhaps 5 if I consider one non-general purpose, personally written). gson is generally very popular as well. The blog post mentions BigDecimal and at that point, I'd not dare to trust it much.
The de-facto standard is similar to the expectation everyone uses spring boot.