Not always. Usually. If you just type MBps vs Mbps into a search engine of your choice, you’ll find quite a few sources that point out that B = Byte and b = bit.

Also, it’s even less always since there are other ways of notating datarate. Here in Germany, for example, Mbps is usually written MBit/s and MB/s stays MB/s. Similar to kph which we write km/h. Also I‘ve seen mbps written (incorrectly) with a lower case 'M' and sometimes with an uppercase M.

Technically Mb/s = Mbps ≠ MBps = MB/s, if you want to stay SI conform.

It’s simply a metric not very well suited for all caps which can cause confusion, if you’re used to different notations.