That was the case with the 2016 and 2017 models of 13" MBP w/touch bar - the right side had reduced PCI Express bandwidth. The 2018 model has full bandwidth on all ports.

Does the 15 have the same problem?

ISTR that the 15” of all generation had 4 lane TB3 ports on both sides. The distinction was the older 13” had two lanes on the right.

It's the 2016/2017 versions of the tbMBP 13". My understanding is that the the right-hand side have all the same capabilities as the left-hand side, but lower PCIe bandwidth.

It's definitely confusing and a bit frustrating that it's different if you're in a scenario where the bandwidth matters, but at least it's just numbers rather than devices outright not working.

I once encountered a situation where a particular projector would only work when connected to the right hand side of my 13" MacBook Pro (2016) - so it's not true to say that devices don't work.