blotchy stain result (old Cabot applied over new low-VOP Cabot)

Hi, thanks for such a great forum...your advice is invaluable! Full/partial sun deck, unsure of wood type, upstate NY. Recently applied old Cabot semi solid stain (1400) over new VOP compliant (17400) that had been put on by previous owner, same color (I read bad things about the 17400 series so found a source for the 1400 product). My handyman sanded, cleaned and pressure washed but there are many small patches where he didn't get all the old product off (he claimed it would be okay...guess not!). These are now showing as small blotches of old matte stain in the midst of the new, nice, penetrating oil stain.

Questions: I can live with this appearance and don't plan to redo the whole deck right now. 1) How will this blotchiness likely wear over time (will those blotches of previous stain wear off, peel, etc?), and 2) will I eventually be able to just clean and reapply a new coat of the 1400 product over the whole deck to even out the color? My understanding is that these penetrating oil products can be redone in this way without sanding, stripping, etc. THANKS!!!