I don't think this is shrinkflation. 100g is a very, very common size for food products as here in Europe foods must have health charts (kcalories, sugars, etc) as both total for the package and per 100g. If the package is 100g it makes that easier and they only need 1 chart, good for smaller products.
This is just a European company selling the same product they sell elsewhere in a region that uses a very stupid measurement system.
It's a mistake in the label template. In variable label printing it is common to use the same template for all products, i would imagine that the weight is probably stored as a floating-point number in the database and it is required to round the number to fit it on the template. It probably looked fine for 99% of labels being printed, especially in the European market where we use the metre SI.. but in this case it did not work out, classic programmers nightmare to handle different locales especially for a company that probably centralize all label printing for all Ikea stores in the world.
That is a possible explanation, but I don't buy it for a simple reason: I don't know of any country where the shelf-label weight is allowed to differ from the actual gross weight by almost 15%. Ikea isn't a small chain that just opened. If you are indeed correct and they simply haven't bothered to update their templates, would really not a single person have sued since they started?
This being a temporary consequence of shrinkflation is far more likely than this being a permanent oversight. Sure, the US is the wild west for consumer rights in many aspects, but not this far.