The problem isn't that SPECTRE's scenes go on too long, it's that Smith has no sense of emotional current and aesthetic pleasure. His editing rhythms are shaped by plot incident, not mood or performance.
His Nolan films display the same problem: they barrel through moments that they should savor just to get to the next big plot point. As a result, everything feels stuck in one gear. (Note also that the film's big, trailer-friendly action moments feel unimpressive in context, another sign of poor editing rhythm.)
The best filmmaking in SPECTRE occurs when Lucia Sciarra braces herself for death. It's not a big story moment, but it's a beautiful grace note full of humanity and aesthetic pleasure. Bond films thrive on those grace notes and SPECTRE needed an editor more attentive to them.
But if Smith repeatedly shows the same issues it's probably his genuine style - and he was likely or not hired for that. Somebody amongst the top brass must like his flavour.
Yes. We know Mendes likes Nolan. Mendes also loved working with Smith, so it's not as though he was unhappy.
That said, I preferred the editing in SKYFALL.