All mechanics used in Celeste that could be considered glitches were intentionally left unpatched by the developers. This means that they are intended behavior, and thus neither glitches, exploits, nor major glitches.
This was on an N3DSXL with Luma3DS 8.1 and NTR 3.5. I was using the memory patch and NFC patch (as they're required for streaming), and I was streaming the whole time NTR was active. Results:
NORMAL: continue: 3.23s/3.26s/3.33s pokemon center entering: 2.38s/2.40s/2.37s houoli city grass patch entering: 3.49s/3.93s/3.88s honey: 9.10s/9.20s/9.15s NTR: continue: 3.35s/3.36s/3.31s pokemon center: 2.45s/2.35s/2.26s houoli city grass patch entering: 4.04s/3.95s/4.00s honey: 9.38s (i hit stop a little slow)/9.14s/9.25s
Do note that, although this cannot be proven, the presumed reason for Gen 6 being faster, is that NTR needs Clock + L2 overclocking mode to stream. Sun/Moon does this by default, even on a stock console.