No, I wouldn't say that's the case. For example, in PHP you can literally write:
if (1 == "1") { ...
This is not the case in strongly typed programming languages that have strings such as C++ or Java. You can convert from one type to another, sure, by explicitly invoking a function like atoi() or Integer.toString(), but the conversion is deliberate and so it is strongly typed. A variable containing a string (java.lang.String) cannot be compared against one containing a timestamp (java.util.Date) by accident. An Ion timestamp is a timestamp and can't be conflated with a string, although it can be converted to one.
Edit: The set of types that are built in, in conjunction with how those types are expressed in programming languages (e.g. timestamp as java.util.Date, decimal as java.math.BigDecimal, blob as byte[]), is why I'd call Ion strongly typed or richly typed in comparison to JSON. Specifically, scalar values that frequently appear in common programs can be expressed with distinctly typed scalar values in Ion. I don't know if there's a good formal definition. You could probably define a preorder on programming languages or data formats based simply on the number of distinct scalar or composite types (so in that sense, yes, it's the fact that Ion has more). However it goes beyond that subjectively. Subjectively it's about how often you have to, in practice, convert from one type to another in common tasks. There is no clear way to represent an arbitrary-precision decimal in JSON, or a byte array, or a timestamp -- so you must "compress" those types down into a single JSON type like string-of-some-format or array-of-number; and several different scalar types must all map to that same JSON type, which creates the risk of conflating values of different logical types but the same physical JSON type with each other. There's no obvious or built-in way to reconstruct the original type with fidelity. There's no self-describing path back from "1999-12-31T23:14:33.079-08:00" and "DEADBEEFBASE64" back to those original types.
I subjectively call JSON weakly typed because its types are not adequately to uniquely store common scalar data types that I work with in programs that I write. I call Ion strongly typed because it typically can. I acknowledged earlier that a data format would be even more strongly typed if it was capable of representing not just the type "integer", but "integer length meters". Ion does not have this kind of type built in, though its annotations feature could be used to describe that a particular integer value represents a length in meters.