Will an angled enclosure effect the sound of a passive radiator?

Depends. All you can do is try it out. At low frequencies the bass should be uniform and move the passive radiator evenly. But since a passive rad has no support other than the front surround in most cases, you can eventually get into a situation of having uneven sagging.

I HAVE seen a slanted baffle box cause a bass wave, a sustained bass note from a synth recording..cause a bass wave to ’walk around’ the periphery of the woofer surround. Yes, a distortion walking around in a circle, modulating the woofer surround in a repeating circular pattern.

This was on a nominal 7" woofer, a sealed two way bookshelf speaker, with a fairly sharply angled baffle.

So it is possible to get a modulation going, one that is uneven.

your problem is that secondary modulations and interference/beat frequencies can and will appear in the box with the angled/sloped baffle. Eventually..something will work in exciting a problem into being, just for the one given recording. If unlucky, you’ve built a easily excitable mode. these problems can occur in standard rectangular construction, but it is just..less likely to be an issue in standard design shapes.

See olson’s work on box shape resonance results in the bass.

https://dt7v1i9vyp3mf.cloudfront.net/styles/news_large/s3/imagelibrary/S/SEEgg150_02-.1o0ooCACPaL5tp...
(the tiny circle in the images is the driver location on the box shape)

(ok. It was an NHT speaker and the song came off a Tangerine dream album. It was the mixing harmonics that did it. https://www.youtube.com/watch?v=AK9zKafP-TA )

I hear exactly what you are saying but, there are secondary concerns, and they have their explanations. Some of this gets into the lore of speaker design, and is generally tightly held as it is part of what can make a speaker company successful, vs reaching up to mediocre by chance. Clarity was purposely not there. :)

I’ll go back to lurking in any speaker discussions, and not increase or create confusion...