As a transistor substitution manual, its language hardly matters. However, most such manuals focus on repairing consumer electronics. Substitutions usually working for consumer electronics may not work where other properties dominate circuit function. For instance, most consumer radio-frequency and intermediate-frequency amplifier transistors are produced with the small-signal frequency response in mind. The substitution working well for a consumer receiver may not work at all for an industrial or even a hobby circuit requiring a high large-signal slew rate.
If a substitution fails to operate well, it may only need a bias resistor value change. If the bias resistor does not resolve the poor performance, perform a side-by-side transistor data-sheet check for differing specifications. Consider whether the differing specifications may be causing the poor performance.