Sure, but you can have the same aspect ratio at the same width with a 16:9 as you can with a 21:9 for roughly the same price or cheaper. As an added bonus, with the 16:9 you have extra vertical resolution if you need it.
I have no problems running games in a 21:9 aspect ratio on my 55" 16:9 display which would be roughly a similar width to a 52" 21:9 display. Only I'd have more vertical resolution if needed.
And since it's OLED, if I'm playing a game in a dark room, guess what? You wouldn't even know there was black bars top and bottom since there's no LCD backlight glow to ruin it. So you would basically have no way of knowing that you aren't actually playing on a 21:9 display.
For similar performing panels, larger 16:9 displays are generally cheaper than smaller 21:9 panels. I can understand not wanting to do what I'm doing with an LCD screen where the backlight glow makes it obvious you aren't using a more expensive but similar performing ultrawide display, but with OLED there is almost no downside to playing in an ultrawide aspect ration on a 16:9 display. And even with the backlight glow of LCD's I still preferred gaming at 21:9 ratios on a 16:9 display ... because it was cheaper for the same performance AND I still had more vertical resolution if I needed it.
Hell, I'd kill for a 3:2, 4:3 or 5:4 ratio OLED display and I'd still be able to benefit from ultrawide gaming if I so desired with almost no drawbacks. Currently the only downsides to doing this is the lack of curved OLED displays or refresh rates higher than 120 Hz. But the curvature is easily rectified if a display manufacturer wanted to make one (LG used to make curved OLED displays). As for the latter, I'm perfectly fine with 120 Hz ... well I would be if I could actually find a graphics card for a resonable price with HDMI 2.1 output.
Hell, looking at LG's displays if I had to choose between a 1,300 USD MSRP 34" ultrawide and a 48" 1,300 USD MSRP 48" OLED display, I know which one I'd choose to buy for ultra-wide gaming ... and it wouldn't be the ultrawide display.
The OLED would give a superior ultrawide gaming experience in an ultrawide aspect ratio in almost all respects. Hell, it has higher horizontal resolution AND width with better HDR and lower pixel response rates.
Regards,
SB