It probably depeds whch basal insulin you use because they last different lengths of time. A very long acting one like Tresiba is very forgiving and can be taken a few hours earlier or later with no noticeable impact.
I used to use Lantus and always found that it is pretty flexible. For me, it can cope with up to 2 hours adjustment in one day.
The shorter acting ones like Levemir may be a bit more sensitive but I would not expect any issues when moving it by 1 hour. Regardless of day light saving, there will be events that could happen which would delay your dose by 30 minutes or more - we don't live our days by clockwork and should no be controlled by our diabetes.
I would see no value moving the timing by 15 minutes - it sounds like unnecessary faff to me.
Just keep a closer eye on your levels on the day you make the change.