I really need an answer why for this one. Is it to make those watches artificially obsolete?
I have Garmin Fenix 3. It has dedicated pool swimming mode and detects laps and swim strokes.
Yes, I know, it has swimming functionality, but not the personal records for swimming functionality. Have a look at the bottom of this website:
https://support.garmin.com/faqSearch/en-US/faq/content/O8rHgFa3iB2HpErPIxL4v5
According to this you will get personal records for swimming only if you have the Fenix 5, the Forerunner 935 or the FR735XT.
Is this still the case that the fenix 3 will not record personal swimming records?
Yes, records, to be shown on Garmin Connect, in the system that is used today, must be supported by the firmware of the watch. And since Fenix 3 is a three generations old watch, I'd tell that it is not very likely that the programmers would spend their time on reprogramming, testing, and deploying new firmware for it.