It’s possible.
https://support.go.goinc.jp/hc/en-us/articles/25883320478745-What-is-Ride-Preferences

But it’s not perfect options because of wheelchair specifications and driver’s skills to set up ramp. Additionally taxies would be Japan Taxi, not Van type vehicle in most cases.
https://global.toyota/en/jpntaxi/

Check if your wheelchair fits on this vehicle;

https://meguritaxi.com/english-carecab-page

Very pleased to hear that our services were helpful during your stay in Tokyo.

It was my pleasure to assist Nick and his wife in enjoying the horse racing in Tokyo. Here is my update about his visit at Tokyo Racecourse.

https://odekakeoffice.jp/en/2024/05/07/tokyo-racecourse/

Much better information than I sent!