Elise and Relic Shield Passive

I was trying elise support, and I came across this weird interaction with human form and relic shield. If you auto attack in human form, and then turn into spider form as soon as the auto goes off, it will count as a melee and execute minions. I've tried this several times and it seems consistant every time I do it. No this isn't last hitting, this is legitimately executing with a ranged attack just before I switched to a melee attacker mid animation.

Steps to repeat:

• Buy a relic shield or any items sharing its passive on Elise .
• Have a teammate with you in order to proc the passive.
• When a minion has enough health to be executed, auto attack it in human form.
• Right as the auto goes off and you see the missile going, before it makes contact with the minion, press r and switch to spider form.
• The auto will count as a melee attack and execute the minion just because you switched to a melee champ even though it was a ranged auto.