Precisely because tool-specialization isn't a good analogue to problem-domain specialization.
e.g. Saying "Ruby Developer" isn't like saying "Brain Surgeon". It's more like saying "Hammer Carpenter" or "Scalpel Surgeon".
Web Developer, Embedded Developer -- these are more akin to specialization on the order of "Brain Surgeon" or "Endocrinologist". Notably, no-one's taking issue with that kind of specialization.
e.g. Saying "Ruby Developer" isn't like saying "Brain Surgeon". It's more like saying "Hammer Carpenter" or "Scalpel Surgeon".
Web Developer, Embedded Developer -- these are more akin to specialization on the order of "Brain Surgeon" or "Endocrinologist". Notably, no-one's taking issue with that kind of specialization.