What doesn't make sense? Saying "A is 50% faster than B" is equivalent to "A is 150% as fast as B". Same goes for "A is 0.5x faster than B" which is equivalent to "A is 1.5x as fast as B".
There is a very distinct difference between "faster than" and "as fast as" which should be very clear now.
You're 100% right (2x right?), but I think this is one of those situations like "bimonthly", where people usually intend it to mean twice a month instead of every two months.
It's completely ambiguous with potentially significant costs for misunderstanding, but people refuse to make themselves clear, just because.
There is a very distinct difference between "faster than" and "as fast as" which should be very clear now.