They replace the adhesive for each repair. The liquid resistance remains the same, so like mentioned above, don't count on it.
Liquid resistance in iPhones (and phones in general) is the last line of defence for liquid damage.
Keep in mind, it is not just the adhesive under the screen. It is the adhesive around the loudspeaker, the earpiece, the mics. These adhesives age, wear and tear overtime from flexing the phone inside the pocket, heat from the sun, cold in the winter.
Don't count on it.