Here's a oddity (I've used extreme tempos to make it clearer):
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https://i.imgur.com/efBk9Et.png
The first track has a quarter note clip at 240 bpm and an eighth note clip at 120 bpm; the length of each note (in ms) is the same, as expected.
The second track shows them glued together and the third track shows the glued clip in the in-line MIDI Editor; both take into account the tempo change.
Below that is the glued clip in the MIIi Editor - you'll see there that the 8th notes are represented at the initial tempo. It looks like the tempo change at bar 8 is not taken into account.