I’m with you! I visit Paris and find that if you try to use some French, they will be very accommodating to you. And if you show some appreciation for Paris - they’ll shake your hand and, as happened to me, kiss your cheek.
Once when I couldn’t get through the Metro turnstyles, a French woman grabbed me and shoved me through on her own card!
Of course, I’m a NYer, so perhaps I am used to city-like behavior.
I visited Paris in 1976/77...my sister and her at the time peignoir(sp) husband (French Algerian) spoke French fluently, luckily. It was not quite as friendly then as you say. But, I’ll bet it’s on a case by case basis, kind of like could happen here in America.