Why rinse flask with distilled water when the flask will be used for storing aliquots of HCl for titration?

In an experiment for standardisation of NaOH with titration, the lab manual instructed students to rinse conical flasks that were supposed to store 1mL aliquots of hydrochloric acid with distilled water.

Won't the excess water dilute the aliquot? Why not rinse with the HCl solution instead?

The dilution with excess water won't affect the total amount of $$\ce{HCl}$$ in the solution, which is what you will be titrating. You still know how much $$\ce{HCl}$$ you have from your quantitative addition of the $$\pu{1 mL}$$ aliquiot. If you rinsed with $$\ce{HCl}$$, you would have no idea how much $$\ce{HCl}$$ you really had and therefore you couldn't calculate the concentration of your $$\ce{NaOH}$$.