I would have thought there would be less EMI when powered from 50Hz, than the 50kHz. It's generally recommended to keep cable runs as short as possible with electronic transformers, to minimise EMI. Quire often, each lamp will have its own transformer, so the cables can be very short. Conventional transformers are less of a problem: just make the cable thick enough, do the voltage drop isn't significant, with the maximum length being determined by the wire gauge which will fit in the terminals.
If the LED lamps are properly designed, they should work over a reasonably wide voltage range, so the slightly higher voltage from a lightly loaded transformer won't be a problem. It should have a switched mode power supply, which will deliver the same current to the LED dies, over a reasonably wide supply voltage range.
Electronic transformers aren't regulated either. They typically consist of a Royer oscillator driving a high frequency transformer, with no feedback. It's possible electronic transformers offer better regulation, than conventional transformers, because they have lower copper losses, but they also have additional losses in the rectifier and transistors. Regulation specifications for conventional transformers are easy to find, but I haven't found any for electronic transformers, so it's not possible to compare, unless one has the time and resources to do the experiments. Here's an SG application note on electronic transformers.
https://www.st.com/content/ccc/resource/technical/document/application_note/e5/88/46/11/35/8c/4a/bf/CD00003902.pdf/files/CD00003902.pdf/jcr:content/translations/en.CD00003902.pdfIt's actually more difficult to design an LED lamp to be compatible with an electronic transformer, compared to a conventional one. Electronic transformers typically require a minimum load current, which is much greater than an LED lamp, so various tricks need to be employed to make it work. This is why I'm surprised this LED is recommended for use with electronic transformers only. Here's a brief presentation I've found on designing LED lamps to work off electronic transformers.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=2ahUKEwiG5-fHmNHkAhXUasAKHcnGC44QFjAKegQIAhAC&url=http%3A%2F%2Fwww.deyisupport.com%2Fcfs-file.ashx%2F__key%2Fcommunityserver-discussions-components-files%2F24%2F7711.Transformer-application.pdf&usg=AOvVaw1O71tqHvjAr0ZlgfiOK-9nI suspect people have problems with short LED lifetimes because they have bought cheap, crappy LEDs. It may be even more of a problem if they're run off an electronic transformer, as the slow rectifier diodes in cheap LED designed for 50Hz, will get much hotter at 50kHz, assuming they use enough to fulfil the minimum load requirement of the transformer, so it actually works.