I ran into this issue with AirBNB - first time I used it last fall. It is clearly dynamic currency conversion - and seriously inflates their fee. I had a series of useless phone calls and email exchanges with AirBNB, citing VISA's policy on dynamic currency conversion - final response from AirBNB here:
"I completely understand your question, however the currency in which you pay in is based on the currency you have set on your profile, as well as on the currency supported by your payment method.
If for example you're paying with a credit card issued in the US, you'll be charged in USD.
I checked your profile and saw that you have the currency on your profile set as USD. I also checked the card that you used to pay for this reservation in question and it was issued in the US as well.
I can assure you that I completely understand your point but unfortunately that is an automated system feature.
I'm really truly sorry about this and I wish I really could do more but unfortunately this is a feature that we are unable to overcome."
At this point, I noticed that the rental I had been in the process of booking - suddenly increased in both price and minimum stay requirement. I contacted the host, who said this was managed by AirBNB. I had very specific needs for a rental, so decided to give up the fight, fearing that not only would I get penalized on price, but that AirBNB could suspend/cancel my account. I'm sorry to say that I buckled, and gave into this "system feature".
Also - in researching options - I realized that Home Away (or VRBO who I have used for YEARS) has followed AirBNB in not only charging a "service fee" but also dynamic currency conversion. I'm a big believer in private home rentals - have done it for more than 20 years for family gatherings - but I think AirBNB has ruined it for all of us.