No, but it's closer than many people think. Let's take a look at the figures quoted for the Miyata tubesets. Their CrMo starts out at a tensile strength of 82 ksi. After brazing it drops to 73 ksi, which is about 91% of the original strength.

For Mangalight it starts out at 72 ksi, but it retains about 97% of it's strength after brazing which works out to 70 ksi. So while Manglight retains a higher percentage of it's original tensile strength, it is still slightly weaker than CrMo after brazing, simply because the initial strength is less. .

By comparison, Miyata's hi-tensile steel starts out at 60 ksi and drops to 50 ksi after brazing, retaining only 83% of its strength.

The above figures are for butted tubes and apply to Miyata's particular tube compositions. Results for other manufacturers will vary slightly.

I can only speculate as to why they stopped making the MnMo tubesets. The road bicycle market has shifted upscale and to materials like aluminum, carbon fibre and titianium. Generally, whenever an industry undergoes a major shift or technological change, the old high end technology becomes the new low end technology and the old, low end technology disappears. I think this is what happened with many of the steel tubests. The old, low end stuff disappeared and only the better sets survived, but lost much of their status. Aluminum has pretty much taken over the market. Steel still survives, but mostly as hi-tensile in the department store bicycles were very low cost is the prime factor and weight is not a concern. Even there, it is under the threat of aluminum.