Isn't that dock connector more like service connector - for flashing firmware, bootloaders etc.. like in other iOS devices?
For anyone who's wondering...
- you can open the iMac without heat gun, using just Plastic Playing Card (poker-like) instead of guitar picks, same results, easier and faster
- you can mount any 9.5mm x 2.5" (or little heigher, there is plenty of space inside) disk - any SSD should work (using Vertex 4)
- any RAM 1600MHz, CL11 should work (using ValueRAM 2x8GB CL11 1600MHz here) and... you don't need to unscrew nor remove the logic board - just unscrew fan, then use toothpicks (yeah, or something sturdier) to unclip RAM, mount new RAM, screw fan and you're done
- removing old tape is simple, it peels off easily, i used 3M 5915 6mm 16mil tape, results are almost perfect, you may find other thin (14mil would be the best) tape with strong glue and foam
PS 7/10 repair score
you can replace with any HD, remove fan, then you can replace ram without removing LB - done myself