The economist doesn’t rely on the testimony of experts at all. If anything, she opposes the testimony of experts by countering her colleagues’ position that interest rates should be lowered.

The economist doesn’t confuse economic growth with what stimulates it; she never argues that lower interest rates are economic growth. She distinguishes between these ideas in her argument, saying that interest rates shouldn’t be lowered and that economic growth is stable.

The economist concludes that there is no reason to lower interest rates simply because she weakened one reason. She ignores other possible reasons for lowering interest rates, assuming that economic stimulation is the only one.

The economist says that economic stimulation isn’t needed because the economy is stable. She never assumes that lowering interest rates is the only way of stimulating the economy. Instead, she assumes that stimulating the economy is the only reason to lower interest rates.

The economist’s conclusion is that there’s no reason to lower interest rates. She doesn’t conclude that further lowering them will cause unstable economic growth. She simply says that further lowering interest rates is unnecessary because economic growth is already stable.